Re-land alexbost's experimental Offscreen Tabs API work.

chrome/browser/extensions/extension_offscreen_tabs_module.cc

Index: chrome/browser/extensions/extension_offscreen_tabs_module.cc
diff --git a/chrome/browser/extensions/extension_offscreen_tabs_module.cc b/chrome/browser/extensions/extension_offscreen_tabs_module.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f9210375c611d55fbeb45c84127ce9afa3cd10ff
--- /dev/null
+++ b/chrome/browser/extensions/extension_offscreen_tabs_module.cc
@@ -0,0 +1,1092 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/extensions/extension_offscreen_tabs_module.h"
+
+#include <algorithm>
+#include <vector>
+
+#include "base/base64.h"
+#include "base/json/json_writer.h"
+#include "base/memory/ref_counted_memory.h"
+#include "base/stl_util.h"
+#include "base/string_number_conversions.h"
+#include "base/string_util.h"
+#include "base/values.h"
+#include "chrome/browser/extensions/extension_event_router.h"
+#include "chrome/browser/extensions/extension_function_dispatcher.h"
+#include "chrome/browser/extensions/extension_host.h"
+#include "chrome/browser/extensions/extension_message_service.h"
+#include "chrome/browser/extensions/extension_offscreen_tabs_module_constants.h"
+#include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/extension_tab_util.h"
+#include "chrome/browser/extensions/extension_tabs_module.h"
+#include "chrome/browser/extensions/extension_tabs_module_constants.h"
+#include "chrome/browser/net/url_fixer_upper.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_navigator.h"
+#include "chrome/browser/ui/browser_window.h"
+#include "chrome/browser/ui/snapshot_tab_helper.h"
+#include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
+#include "chrome/browser/ui/window_sizer.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/extensions/extension.h"
+#include "chrome/common/extensions/extension_error_utils.h"
+#include "chrome/common/extensions/extension_messages.h"
+#include "chrome/common/pref_names.h"
+#include "chrome/common/url_constants.h"
+#include "content/browser/renderer_host/backing_store.h"
+#include "content/browser/renderer_host/render_view_host.h"
+#include "content/public/browser/navigation_controller.h"
+#include "content/public/browser/navigation_entry.h"
+#include "content/public/browser/notification_details.h"
+#include "content/public/browser/notification_source.h"
+#include "content/public/browser/render_view_host_delegate.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_view.h"
+#include "skia/ext/image_operations.h"
+#include "skia/ext/platform_canvas.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+
+using content::NavigationController;
+using content::NavigationEntry;
+using content::NotificationDetails;
+using content::NotificationSource;
+using WebKit::WebInputEvent;
+
+namespace keys = extension_offscreen_tabs_module_constants;
+namespace tabs_keys = extension_tabs_module_constants;
+
+namespace {
+
+class ParentTab;
+
+// Offscreen Tab ---------------------------------------------------------------
+
+// This class is responsible for the creation and destruction of offscreen tabs,
+// as well as dispatching an onUpdated event.
+class OffscreenTab : public content::NotificationObserver {
+ public:
+  OffscreenTab();
+  virtual ~OffscreenTab();
+  void Init(const GURL& url,
+            const int width,
+            const int height,
+            Profile* profile,
+            ParentTab* parent_tab);
+
+  TabContentsWrapper* tab() { return tab_.get(); }
+  content::WebContents* contents() { return tab_.get()->web_contents(); }
+  ParentTab* parent_tab() { return parent_tab_; }
+  DictionaryValue* CreateValue();  // Creates an offscreen tab object returned
+                                   // by the API methods.
+                                   // The caller owns the returned value.
+
+  void SetURL(const GURL& url);
+  void SetSize(int width, int height);
+
+ private:
+  virtual void Observe(int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+  content::NotificationRegistrar registrar_;
+
+  scoped_ptr<TabContentsWrapper> tab_;  // TabContentsWrapper associated with
+                                        // this offscreen tab.
+  ParentTab* parent_tab_;
+
+  DISALLOW_COPY_AND_ASSIGN(OffscreenTab);
+};
+
+typedef std::vector<OffscreenTab*> TabVector;
+typedef TabVector::iterator TabIterator;
+typedef TabVector::const_iterator ConstTabIterator;
+
+// ParentTab -------------------------------------------------------------------
+
+// Holds info about a tab that has spawned at least one offscreen tab.
+// Each ParentTab keeps track of its child offscreen tabs. The ParentTab is also
+// responsible for killing its children when it navigates away or gets closed.
+class ParentTab : public content::NotificationObserver {
+ public:
+  ParentTab();
+  virtual ~ParentTab();
+  void Init(content::WebContents* web_contents,
+            const std::string& extension_id);
+
+  TabContentsWrapper* tab() { return tab_; }
+  content::WebContents* contents() { return tab_->web_contents(); }
+  const TabVector& offscreen_tabs() { return offscreen_tabs_; }
+  const std::string& extension_id() const { return extension_id_; }
+
+  // Tab takes ownership of OffscreenTab.
+  void AddOffscreenTab(OffscreenTab *tab);
+  // This deletes the OffscreenTab.
+  void RemoveOffscreenTab(OffscreenTab *tab);
+
+ private:
+  virtual void Observe(int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+  content::NotificationRegistrar registrar_;
+
+  TabContentsWrapper* tab_;  // TabContentsWrapper associated with this tab.
+  TabVector offscreen_tabs_;  // Offscreen tabs spawned by this tab.
+  std::string extension_id_;  // Id of the extension running in this tab.
+
+  DISALLOW_COPY_AND_ASSIGN(ParentTab);
+};
+
+// Map -------------------------------------------------------------------------
+
+// This map keeps track of all tabs that are happy parents of offscreen tabs.
+class Map {
+ public:
+  Map();
+  ~Map();
+
+  // Gets an offscreen tab by ID.
+  bool GetOffscreenTab(const int offscreen_tab_id,
+                       ExtensionFunctionDispatcher* dispatcher,
+                       Profile* profile,
+                       OffscreenTab** offscreen_tab,
+                       std::string* error_message);
+  // Gets a parent tab by ID.
+  bool GetParentTab(const int parent_tab_id,
+                    ParentTab** tab,
+                    std::string* error_message);
+  // Creates a mapping between a parent tab and an offscreen tab.
+  bool AddOffscreenTab(OffscreenTab* offscreen_tab,
+                       const GURL& url,
+                       const int width,
+                       const int height,
+                       Profile* profile,
+                       ExtensionFunctionDispatcher* dispatcher,
+                       const std::string& ext_id,
+                       std::string* error_message);
+  // Removes the mapping between a parent tab and an offscreen tab.
+  // May cause the Tab object associated with the parent to be deleted.
+  bool RemoveOffscreenTab(const int offscreen_tab_id,
+                          ExtensionFunctionDispatcher* dispatcher,
+                          Profile* profile,
+                          std::string* error_message);
+  // Removes a parent tab from the map along with its child offscreen tabs.
+  // It is called by the destructor of a ParentTab.
+  bool RemoveParentTab(const int parent_tab_id, std::string* error_message);
+
+ private:
+  typedef base::hash_map<int, ParentTab*> TabMap;
+  TabMap map;
+
+  DISALLOW_COPY_AND_ASSIGN(Map);
+};
+
+// Variables -------------------------------------------------------------------
+
+Map* map = NULL;
+
+// We are assuming that offscreen tabs will not be created by background pages
+// with the exception of the API test background page. We keep track of the
+// offscreen tabs associated with the test API background page via this variable
+// These tab contents are created just for convenience and do not do anything.
+// TODO(alexbost): Think about handling multiple background pages each spawning
+// offscreen tabs. Would background pages want to spawn offscreen tabs?
+// If not, we need to somehow distinguish between the test background page and
+// regular background pages and disallow offscreen tab creation for the latter.
+content::WebContents* background_page_web_contents = NULL;
+
+// Util ------------------------------------------------------------------------
+
+// Gets the map of parent tabs to offscreen tabs.
+Map* GetMap() {
+  if (map == NULL)
+    map = new Map();
+
+  return map;
+}
+
+// Gets the WebContents associated with the test API background page.
+content::WebContents* GetBackgroundPageWebContents(Profile* profile) {
+  if (background_page_web_contents == NULL) {
+    background_page_web_contents =
+        content::WebContents::Create(
+            profile, NULL, MSG_ROUTING_NONE, NULL, NULL);
+    new TabContentsWrapper(background_page_web_contents);
+  }
+
+  return background_page_web_contents;
+}
+
+// Gets the WebContents of the tab that instantiated the extension API call.
+// In the case of background pages we use WebContents created by us.
+bool GetCurrentWebContents(ExtensionFunctionDispatcher* dispatcher,
+                           Profile* profile,
+                           content::WebContents** web_contents,
+                           std::string* error_message) {
+  *web_contents = dispatcher->delegate()->GetAssociatedWebContents();
+
+  // Background page (no associated tab contents).
+  if (!*web_contents)
+    *web_contents = GetBackgroundPageWebContents(profile);
+
+  if (*web_contents)
+    return true;
+
+  *error_message = keys::kCurrentTabNotFound;
+  return false;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+// Takes |url_string| and returns a GURL which is either valid and absolute
+// or invalid. If |url_string| is not directly interpretable as a valid (it is
+// likely a relative URL) an attempt is made to resolve it. |extension| is
+// provided so it can be resolved relative to its extension base
+// (chrome-extension://<id>/). Using the source frame url would be more correct,
+// but because the api shipped with urls resolved relative to their extension
+// base, we decided it wasn't worth breaking existing extensions to fix.
+GURL ResolvePossiblyRelativeURL(const std::string& url_string,
+                                const Extension* extension) {
+  GURL url = GURL(url_string);
+  if (!url.is_valid())
+    url = extension->GetResourceURL(url_string);
+
+  return url;
+}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+bool IsCrashURL(const GURL& url) {
+  // Check a fixed-up URL, to normalize the scheme and parse hosts correctly.
+  GURL fixed_url =
+      URLFixerUpper::FixupURL(url.possibly_invalid_spec(), std::string());
+  return (fixed_url.SchemeIs(chrome::kChromeUIScheme) &&
+          (fixed_url.host() == chrome::kChromeUIBrowserCrashHost ||
+           fixed_url.host() == chrome::kChromeUICrashHost));
+}
+
+// Offscreen Tab ---------------------------------------------------------------
+
+OffscreenTab::OffscreenTab()
+    : parent_tab_(NULL) {
+}
+
+OffscreenTab::~OffscreenTab() {}
+
+void OffscreenTab::Init(const GURL& url,
+                        const int width,
+                        const int height,
+                        Profile* profile,
+                        ParentTab* parent_tab) {
+  // Create the offscreen tab.
+  content::WebContents* web_contents = content::WebContents::Create(
+      profile, NULL, MSG_ROUTING_NONE, NULL, NULL);
+  tab_.reset(new TabContentsWrapper(web_contents));
+
+  SetSize(width, height);  // Setting the size starts the renderer.
+  SetURL(url);
+  parent_tab_ = parent_tab;
+
+  // Register for tab notifications.
+  registrar_.Add(
+      this,
+      content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+      content::Source<NavigationController>(&(contents()->GetController())));
+}
+
+DictionaryValue* OffscreenTab::CreateValue() {
+  DictionaryValue* result = new DictionaryValue();
+
+  result->SetInteger(tabs_keys::kIdKey, ExtensionTabUtil::GetTabId(contents()));
+  result->SetString(tabs_keys::kUrlKey, contents()->GetURL().spec());
+  result->SetInteger(tabs_keys::kWidthKey,
+      contents()->GetView()->GetContainerSize().width());
+  result->SetInteger(tabs_keys::kHeightKey,
+      contents()->GetView()->GetContainerSize().height());
+
+  return result;
+}
+
+void OffscreenTab::SetURL(const GURL& url) {
+  contents()->GetController().LoadURL(
+      url, content::Referrer(), content::PAGE_TRANSITION_LINK, std::string());
+}
+
+void OffscreenTab::SetSize(int width, int height) {
+  contents()->GetView()->SizeContents(gfx::Size(width, height));
+}
+
+void OffscreenTab::Observe(int type,
+                           const NotificationSource& source,
+                           const NotificationDetails& details) {
+  DCHECK_EQ(content::NOTIFICATION_NAV_ENTRY_COMMITTED, type);
+
+  DictionaryValue* changed_properties = new DictionaryValue();
+  changed_properties->SetString(
+      tabs_keys::kUrlKey, contents()->GetURL().spec());
+
+  ListValue args;
+  args.Append(
+      Value::CreateIntegerValue(ExtensionTabUtil::GetTabId(contents())));
+  args.Append(changed_properties);
+  args.Append(CreateValue());
+  std::string json_args;
+  base::JSONWriter::Write(&args, false, &json_args);
+
+  ListValue event_args;
+  event_args.Set(0, Value::CreateStringValue(keys::kEventOnUpdated));
+  event_args.Set(1, Value::CreateStringValue(json_args));
+
+  // Dispatch an onUpdated event.
+  // The primary use case for broadcasting the event is
+  // when the offscreen tab is generated by a test API background page.
+  if (parent_tab_->contents() == background_page_web_contents) {
+    Profile* profile = parent_tab_->tab()->profile();
+    profile->GetExtensionEventRouter()->DispatchEventToRenderers(
+        keys::kEventOnUpdated, json_args, profile, GURL());
+  } else {
+    // Send a routed event directly to the parent tab.
+    if (parent_tab_->contents()->GetRenderViewHost() &&
+        parent_tab_->contents()->GetRenderViewHost()->process())
+      parent_tab_->contents()->GetRenderViewHost()->Send(
+          new ExtensionMsg_MessageInvoke(
+              parent_tab_->contents()->GetRenderViewHost()->routing_id(),
+              parent_tab_->extension_id(),
+              keys::kDispatchEvent,
+              event_args,
+              GURL()));
+  }
+}
+
+// ParentTab -------------------------------------------------------------------
+
+ParentTab::ParentTab()
+    : tab_(NULL) {
+}
+
+ParentTab::~ParentTab() {
+  // Kill child offscreen tabs.
+  STLDeleteElements(&offscreen_tabs_);
+
+  bool removed = GetMap()->RemoveParentTab(
+      ExtensionTabUtil::GetTabId(contents()), new std::string());
+  DCHECK(removed);
+}
+
+void ParentTab::Init(content::WebContents* web_contents,
+                     const std::string& extension_id) {
+  DCHECK(web_contents);
+
+  tab_ = TabContentsWrapper::GetCurrentWrapperForContents(web_contents);
+  DCHECK(tab_);
+
+  extension_id_ = extension_id;
+
+  // Register for tab notifications.
+  registrar_.Add(
+      this,
+      content::NOTIFICATION_NAV_ENTRY_COMMITTED,
+      content::Source<NavigationController>(&(contents()->GetController())));
+
+  registrar_.Add(
+      this,
+      content::NOTIFICATION_WEB_CONTENTS_DESTROYED,
+      content::Source<content::WebContents>(contents()));
+}
+
+void ParentTab::AddOffscreenTab(OffscreenTab *offscreen_tab) {
+  offscreen_tabs_.push_back(offscreen_tab);
+}
+
+void ParentTab::RemoveOffscreenTab(OffscreenTab *offscreen_tab) {
+  TabIterator it_tab = std::find(
+      offscreen_tabs_.begin(), offscreen_tabs_.end(), offscreen_tab);
+  offscreen_tabs_.erase(it_tab);
+
+  delete offscreen_tab;
+}
+
+void ParentTab::Observe(int type,
+                        const NotificationSource& source,
+                        const NotificationDetails& details) {
+  DCHECK(type == content::NOTIFICATION_NAV_ENTRY_COMMITTED ||
+         type == content::NOTIFICATION_WEB_CONTENTS_DESTROYED);
+
+  delete this;
+}
+
+// Map -------------------------------------------------------------------------
+
+Map::Map() {}
+Map::~Map() {}
+
+bool Map::GetOffscreenTab(const int offscreen_tab_id,
+                          ExtensionFunctionDispatcher* dispatcher,
+                          Profile* profile,
+                          OffscreenTab** offscreen_tab,
+                          std::string* error_message) {
+  // Ensure that the current tab is the parent of the offscreen tab.
+  content::WebContents* web_contents = NULL;
+  if (!GetCurrentWebContents(dispatcher, profile, &web_contents, error_message))
+    return false;
+
+  ParentTab* parent_tab = NULL;
+  if (!GetParentTab(
+      ExtensionTabUtil::GetTabId(web_contents), &parent_tab, error_message))
+    return false;
+
+  const TabVector& offscreen_tabs = parent_tab->offscreen_tabs();
+
+  for (ConstTabIterator it = offscreen_tabs.begin();
+      it != offscreen_tabs.end(); ++it) {
+    if (ExtensionTabUtil::GetTabId((*it)->contents()) == offscreen_tab_id) {
+      *offscreen_tab = *it;
+      return true;
+    }
+  }
+
+  *error_message = ExtensionErrorUtils::FormatErrorMessage(
+      keys::kOffscreenTabNotFoundError, base::IntToString(offscreen_tab_id));
+  return false;
+}
+
+bool Map::GetParentTab(const int parent_tab_id,
+                       ParentTab** parent_tab,
+                       std::string* error_message) {
+  TabMap::iterator it = map.find(parent_tab_id);
+
+  if (it == map.end()) {
+    *error_message = ExtensionErrorUtils::FormatErrorMessage(
+        tabs_keys::kTabNotFoundError, base::IntToString(parent_tab_id));
+    return false;
+  }
+
+  *parent_tab = it->second;
+
+  return true;
+}
+
+bool Map::AddOffscreenTab(OffscreenTab* offscreen_tab,
+                          const GURL& url,
+                          const int width,
+                          const int height,
+                          Profile* profile,
+                          ExtensionFunctionDispatcher* dispatcher,
+                          const std::string& ext_id,
+                          std::string* error_message) {
+  // Get parent tab.
+  content::WebContents* web_contents = NULL;
+  if (!GetCurrentWebContents(dispatcher, profile, &web_contents, error_message))
+    return false;
+  int offscreen_tab_id = ExtensionTabUtil::GetTabId(web_contents);
+
+  ParentTab* parent_tab = NULL;
+  if (!GetParentTab(offscreen_tab_id, &parent_tab, error_message)) {
+    parent_tab = new ParentTab();
+    parent_tab->Init(web_contents, ext_id);
+
+    map[offscreen_tab_id] = parent_tab;
+  }
+
+  offscreen_tab->Init(url, width, height, profile, parent_tab);
+
+  // Add child to parent.
+  parent_tab->AddOffscreenTab(offscreen_tab);
+
+  return true;
+}
+
+bool Map::RemoveOffscreenTab(const int offscreen_tab_id,
+                             ExtensionFunctionDispatcher* dispatcher,
+                             Profile* profile,
+                             std::string* error_message) {
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetOffscreenTab(offscreen_tab_id, dispatcher, profile,
+                       &offscreen_tab, error_message))
+    return false;
+
+  ParentTab* parent_tab = offscreen_tab->parent_tab();
+
+  parent_tab->RemoveOffscreenTab(offscreen_tab);
+  offscreen_tab = NULL;
+
+  // If this was the last offscreen tab for the parent tab, remove the parent.
+  if (parent_tab->offscreen_tabs().empty())
+    delete parent_tab;  // Causes tab to be removed from the map!
+
+  return true;
+}
+
+bool Map::RemoveParentTab(const int parent_tab_id, std::string* error_message) {
+  if (map.find(parent_tab_id) == map.end()) {
+    *error_message = ExtensionErrorUtils::FormatErrorMessage(
+        tabs_keys::kTabNotFoundError, base::IntToString(parent_tab_id));
+    return false;
+  }
+
+  map.erase(parent_tab_id);
+
+  return true;
+}
+
+bool CopyModifiers(const DictionaryValue* js_event,
+                   WebKit::WebInputEvent* event) {
+  bool alt_key = false;
+  if (js_event->HasKey(keys::kEventAltKeyKey)) {
+    if (!js_event->GetBoolean(keys::kEventAltKeyKey, &alt_key))
+      return false;
+  }
+  if (alt_key)
+    event->modifiers |= WebInputEvent::AltKey;
+
+  bool ctrl_key = false;
+  if (js_event->HasKey(keys::kEventCtrlKeyKey)) {
+    if (!js_event->GetBoolean(keys::kEventCtrlKeyKey, &ctrl_key))
+      return false;
+  }
+  if (ctrl_key)
+    event->modifiers |= WebInputEvent::ControlKey;
+
+  bool meta_key = false;
+  if (js_event->HasKey(keys::kEventMetaKeyKey)) {
+    if (!js_event->GetBoolean(keys::kEventMetaKeyKey, &meta_key))
+      return false;
+  }
+  if (meta_key)
+    event->modifiers |= WebInputEvent::MetaKey;
+
+  bool shift_key;
+  if (js_event->HasKey(keys::kEventShiftKeyKey)) {
+    if (!js_event->GetBoolean(keys::kEventShiftKeyKey, &shift_key))
+      return false;
+  }
+  if (shift_key)
+    event->modifiers |= WebInputEvent::ShiftKey;
+  return true;
+}
+
+}  // namespace
+
+// API functions ---------------------------------------------------------------
+
+// create ----------------------------------------------------------------------
+
+CreateOffscreenTabFunction::CreateOffscreenTabFunction() {}
+CreateOffscreenTabFunction::~CreateOffscreenTabFunction() {}
+
+bool CreateOffscreenTabFunction::RunImpl() {
+  DictionaryValue* create_props;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(0, &create_props));
+
+  std::string url_string;
+  GURL url;
+  EXTENSION_FUNCTION_VALIDATE(
+      create_props->GetString(tabs_keys::kUrlKey, &url_string));
+  url = ResolvePossiblyRelativeURL(url_string, GetExtension());
+  if (!url.is_valid()) {
+    error_ = ExtensionErrorUtils::FormatErrorMessage(
+        tabs_keys::kInvalidUrlError, url_string);
+    return false;
+  }
+  if (IsCrashURL(url)) {
+    error_ = tabs_keys::kNoCrashBrowserError;
+    return false;
+  }
+
+  gfx::Rect window_bounds;
+  if (!create_props->HasKey(tabs_keys::kWidthKey) ||
+      !create_props->HasKey(tabs_keys::kHeightKey)) {
+    Browser* browser = GetCurrentBrowser();
+    if (!browser) {
+      error_ = tabs_keys::kNoCurrentWindowError;
+      return false;
+    }
+
+    WindowSizer::GetBrowserWindowBounds(std::string(), gfx::Rect(),
+                                        browser, &window_bounds);
+  }
+
+  int width = window_bounds.width();
+  if (create_props->HasKey(tabs_keys::kWidthKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        create_props->GetInteger(tabs_keys::kWidthKey, &width));
+
+  int height = window_bounds.height();
+  if (create_props->HasKey(tabs_keys::kHeightKey))
+    EXTENSION_FUNCTION_VALIDATE(
+        create_props->GetInteger(tabs_keys::kHeightKey, &height));
+
+  OffscreenTab* offscreen_tab = new OffscreenTab();
+
+  // Add the offscreen tab to the map so we don't lose track of it.
+  if (!GetMap()->AddOffscreenTab(offscreen_tab, url, width, height, profile_,
+                                 dispatcher(), extension_id(), &error_)) {
+    delete offscreen_tab;  // Prevent leaking of offscreen tab.
+    return false;
+  }
+
+  // TODO(alexbost): Maybe the callback is called too soon. It should probably
+  // be called once we have navigated to the url.
+  if (has_callback()) {
+    result_.reset(offscreen_tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// get -------------------------------------------------------------------------
+
+GetOffscreenTabFunction::GetOffscreenTabFunction() {}
+GetOffscreenTabFunction::~GetOffscreenTabFunction() {}
+
+bool GetOffscreenTabFunction::RunImpl() {
+  int offscreen_tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &offscreen_tab_id));
+
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetMap()->
+      GetOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                      &offscreen_tab, &error_)) {
+    error_ = ExtensionErrorUtils::FormatErrorMessage(
+        keys::kOffscreenTabNotFoundError, base::IntToString(offscreen_tab_id));
+    return false;
+  }
+
+  if (has_callback()) {
+    result_.reset(offscreen_tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// getAll ----------------------------------------------------------------------
+
+GetAllOffscreenTabFunction::GetAllOffscreenTabFunction() {}
+GetAllOffscreenTabFunction::~GetAllOffscreenTabFunction() {}
+
+bool GetAllOffscreenTabFunction::RunImpl() {
+  content::WebContents* web_contents = NULL;
+  if (!GetCurrentWebContents(dispatcher(), profile_, &web_contents, &error_))
+    return false;
+
+  ParentTab* parent_tab = NULL;
+  if (!GetMap()->
+      GetParentTab(ExtensionTabUtil::GetTabId(web_contents),
+                                              &parent_tab, &error_))
+    return false;
+
+  const TabVector& offscreen_tabs = parent_tab->offscreen_tabs();
+
+  ListValue* tab_list = new ListValue();
+  for (ConstTabIterator it_tab = offscreen_tabs.begin();
+      it_tab != offscreen_tabs.end(); ++it_tab)
+    tab_list->Append((*it_tab)->CreateValue());
+
+  if (has_callback()) {
+    result_.reset(tab_list);
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// remove ----------------------------------------------------------------------
+
+RemoveOffscreenTabFunction::RemoveOffscreenTabFunction() {}
+RemoveOffscreenTabFunction::~RemoveOffscreenTabFunction() {}
+
+bool RemoveOffscreenTabFunction::RunImpl() {
+  int offscreen_tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &offscreen_tab_id));
+
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetMap()->GetOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                                 &offscreen_tab, &error_))
+    return false;
+
+  if (!GetMap()->RemoveOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                                    &error_))
+    return false;
+
+  return true;
+}
+
+// sendKeyboardEvent -----------------------------------------------------------
+
+SendKeyboardEventOffscreenTabFunction::
+    SendKeyboardEventOffscreenTabFunction() {}
+SendKeyboardEventOffscreenTabFunction::
+    ~SendKeyboardEventOffscreenTabFunction() {}
+
+bool SendKeyboardEventOffscreenTabFunction::RunImpl() {
+  int offscreen_tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &offscreen_tab_id));
+
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetMap()->GetOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                                 &offscreen_tab, &error_))
+    return false;
+
+  // JavaScript KeyboardEvent.
+  DictionaryValue* js_keyboard_event = NULL;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &js_keyboard_event));
+
+  NativeWebKeyboardEvent keyboard_event;
+
+  std::string type;
+  if (js_keyboard_event->HasKey(keys::kEventTypeKey)) {
+    EXTENSION_FUNCTION_VALIDATE(
+        js_keyboard_event->GetString(keys::kEventTypeKey, &type));
+  } else {
+    error_ = keys::kInvalidKeyboardEventObjectError;
+    return false;
+  }
+
+  if (type.compare(keys::kKeyboardEventTypeValueKeypress) == 0) {
+    keyboard_event.type = WebInputEvent::Char;
+  } else if (type.compare(keys::kKeyboardEventTypeValueKeydown) == 0) {
+    keyboard_event.type = WebInputEvent::KeyDown;
+  } else if (type.compare(keys::kKeyboardEventTypeValueKeyup) == 0) {
+    keyboard_event.type = WebInputEvent::KeyUp;
+  } else {
+    error_ = keys::kInvalidKeyboardEventObjectError;
+    return false;
+  }
+
+  int key_code;
+  if (js_keyboard_event->HasKey(keys::kKeyboardEventKeyCodeKey)) {
+    EXTENSION_FUNCTION_VALIDATE(js_keyboard_event->
+        GetInteger(keys::kKeyboardEventKeyCodeKey, &key_code));
+    keyboard_event.nativeKeyCode = key_code;
+    keyboard_event.windowsKeyCode = key_code;
+    keyboard_event.setKeyIdentifierFromWindowsKeyCode();
+  }
+
+  // Keypress = type character
+  if (type.compare(keys::kKeyboardEventTypeValueKeypress) == 0) {
+    int char_code;
+    if (js_keyboard_event->HasKey(keys::kKeyboardEventCharCodeKey)) {
+      EXTENSION_FUNCTION_VALIDATE(js_keyboard_event->
+          GetInteger(keys::kKeyboardEventCharCodeKey, &char_code));
+      keyboard_event.text[0] = char_code;
+      keyboard_event.unmodifiedText[0] = char_code;
+    } else {
+      error_ = keys::kInvalidKeyboardEventObjectError;
+      return false;
+    }
+  }
+
+  EXTENSION_FUNCTION_VALIDATE(
+      CopyModifiers(js_keyboard_event, &keyboard_event));
+
+  // Forward the event.
+  offscreen_tab->contents()->GetRenderViewHost()->
+      ForwardKeyboardEvent(keyboard_event);
+
+  if (has_callback()) {
+    result_.reset(offscreen_tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// sendMouseEvent --------------------------------------------------------------
+
+SendMouseEventOffscreenTabFunction::SendMouseEventOffscreenTabFunction() {}
+SendMouseEventOffscreenTabFunction::~SendMouseEventOffscreenTabFunction() {}
+
+bool SendMouseEventOffscreenTabFunction::RunImpl() {
+  int offscreen_tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &offscreen_tab_id));
+
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetMap()->GetOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                                 &offscreen_tab, &error_))
+    return false;
+
+  // JavaScript MouseEvent.
+  DictionaryValue* js_mouse_event = NULL;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &js_mouse_event));
+
+  std::string type;
+  if (js_mouse_event->HasKey(keys::kEventTypeKey)) {
+    EXTENSION_FUNCTION_VALIDATE(
+        js_mouse_event->GetString(keys::kEventTypeKey, &type));
+  } else {
+    error_ = keys::kInvalidMouseEventObjectError;
+    return false;
+  }
+
+  if (type.compare(keys::kMouseEventTypeValueMousewheel) == 0) {
+    WebKit::WebMouseWheelEvent wheel_event;
+
+    wheel_event.type = WebInputEvent::MouseWheel;
+
+    if (js_mouse_event->HasKey(keys::kMouseEventWheelDeltaXKey) &&
+        js_mouse_event->HasKey(keys::kMouseEventWheelDeltaYKey)) {
+      int delta_x, delta_y;
+      EXTENSION_FUNCTION_VALIDATE(js_mouse_event->
+          GetInteger(keys::kMouseEventWheelDeltaXKey, &delta_x));
+      EXTENSION_FUNCTION_VALIDATE(js_mouse_event->
+          GetInteger(keys::kMouseEventWheelDeltaYKey, &delta_y));
+      wheel_event.deltaX = delta_x;
+      wheel_event.deltaY = delta_y;
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    // Forward the event.
+    offscreen_tab->contents()->GetRenderViewHost()->
+        ForwardWheelEvent(wheel_event);
+  } else {
+    WebKit::WebMouseEvent mouse_event;
+
+    if (type.compare(keys::kMouseEventTypeValueMousedown) == 0 ||
+        type.compare(keys::kMouseEventTypeValueClick) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseDown;
+    } else if (type.compare(keys::kMouseEventTypeValueMouseup) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseUp;
+    } else if (type.compare(keys::kMouseEventTypeValueMousemove) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseMove;
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    int button;
+    if (js_mouse_event->HasKey(keys::kMouseEventButtonKey)) {
+      EXTENSION_FUNCTION_VALIDATE(
+          js_mouse_event->GetInteger(keys::kMouseEventButtonKey, &button));
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    if (button == keys::kMouseEventButtonValueLeft) {
+      mouse_event.button = WebKit::WebMouseEvent::ButtonLeft;
+    } else if (button == keys::kMouseEventButtonValueMiddle) {
+      mouse_event.button = WebKit::WebMouseEvent::ButtonMiddle;
+    } else if (button == keys::kMouseEventButtonValueRight) {
+      mouse_event.button = WebKit::WebMouseEvent::ButtonRight;
+    } else {
+      error_ = keys::kInvalidMouseEventObjectError;
+      return false;
+    }
+
+    if (HasOptionalArgument(2) && HasOptionalArgument(3)) {
+      EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(2, &mouse_event.x));
+      EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(3, &mouse_event.y));
+    } else {
+      error_ = keys::kNoMouseCoordinatesError;
+      return false;
+    }
+
+    EXTENSION_FUNCTION_VALIDATE(CopyModifiers(js_mouse_event, &mouse_event));
+
+    mouse_event.clickCount = 1;
+
+    // Forward the event.
+    offscreen_tab->contents()->GetRenderViewHost()->
+        ForwardMouseEvent(mouse_event);
+
+    // If the event is a click,
+    // fire a mouseup event in addition to the mousedown.
+    if (type.compare(keys::kMouseEventTypeValueClick) == 0) {
+      mouse_event.type = WebKit::WebInputEvent::MouseUp;
+      offscreen_tab->contents()->GetRenderViewHost()->
+          ForwardMouseEvent(mouse_event);
+    }
+  }
+
+  if (has_callback()) {
+    result_.reset(offscreen_tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}
+
+// toDataUrl -------------------------------------------------------------------
+
+ToDataUrlOffscreenTabFunction::ToDataUrlOffscreenTabFunction() {}
+ToDataUrlOffscreenTabFunction::~ToDataUrlOffscreenTabFunction() {}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+// TODO(alexbost): We want to optimize this function in order to get more image
+// updates on the browser side. One improvement would be to implement another
+// hash map in order to get offscreen tabs in O(1).
+bool ToDataUrlOffscreenTabFunction::RunImpl() {
+  int offscreen_tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &offscreen_tab_id));
+
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetMap()->GetOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                                 &offscreen_tab, &error_))
+    return false;
+
+  image_format_ = FORMAT_JPEG;  // Default format is JPEG.
+  image_quality_ = kDefaultQuality;  // Default quality setting.
+
+  if (HasOptionalArgument(1)) {
+    DictionaryValue* options;
+    EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &options));
+
+    if (options->HasKey(tabs_keys::kFormatKey)) {
+      std::string format;
+      EXTENSION_FUNCTION_VALIDATE(
+          options->GetString(tabs_keys::kFormatKey, &format));
+
+      if (format == tabs_keys::kFormatValueJpeg) {
+        image_format_ = FORMAT_JPEG;
+      } else if (format == tabs_keys::kFormatValuePng) {
+        image_format_ = FORMAT_PNG;
+      } else {
+        // Schema validation should make this unreachable.
+        EXTENSION_FUNCTION_VALIDATE(0);
+      }
+    }
+
+    if (options->HasKey(tabs_keys::kQualityKey)) {
+      EXTENSION_FUNCTION_VALIDATE(
+          options->GetInteger(tabs_keys::kQualityKey, &image_quality_));
+    }
+  }
+
+  // captureVisibleTab() can return an image containing sensitive information
+  // that the browser would otherwise protect.  Ensure the extension has
+  // permission to do this.
+  if (!GetExtension()->
+      CanCaptureVisiblePage(offscreen_tab->contents()->GetURL(), &error_))
+    return false;
+
+// The backing store approach works on Linux but not on Mac.
+// TODO(alexbost): Test on Windows
+#if !defined(OS_MACOSX)
+  RenderViewHost* render_view_host =
+      offscreen_tab->contents()->GetRenderViewHost();
+
+  // If a backing store is cached for the tab we want to capture,
+  // and it can be copied into a bitmap, then use it to generate the image.
+  BackingStore* backing_store = render_view_host->GetBackingStore(false);
+  if (backing_store && CaptureSnapshotFromBackingStore(backing_store))
+    return true;
+#endif
+
+  // Ask the renderer for a snapshot of the tab.
+  TabContentsWrapper* tab_wrapper = offscreen_tab->tab();
+  tab_wrapper->snapshot_tab_helper()->CaptureSnapshot();
+  registrar_.Add(
+      this,
+      chrome::NOTIFICATION_TAB_SNAPSHOT_TAKEN,
+      content::Source<TabContentsWrapper>(tab_wrapper));
+
+  AddRef();  // Balanced in ToDataUrlOffscreenTabFunction::Observe().
+
+  return true;
+}
+
+// update ----------------------------------------------------------------------
+
+UpdateOffscreenTabFunction::UpdateOffscreenTabFunction() {}
+UpdateOffscreenTabFunction::~UpdateOffscreenTabFunction() {}
+
+// TODO(alexbost): Needs refactoring. Similar method in extension_tabs_module.
+bool UpdateOffscreenTabFunction::RunImpl() {
+  int offscreen_tab_id;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetInteger(0, &offscreen_tab_id));
+
+  OffscreenTab* offscreen_tab = NULL;
+  if (!GetMap()->GetOffscreenTab(offscreen_tab_id, dispatcher(), profile_,
+                                 &offscreen_tab, &error_))
+    return false;
+
+  DictionaryValue* update_props;
+  EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &update_props));
+
+  // Url
+  if (update_props->HasKey(tabs_keys::kUrlKey)) {
+    std::string url_string;
+    GURL url;
+    EXTENSION_FUNCTION_VALIDATE(
+        update_props->GetString(tabs_keys::kUrlKey, &url_string));
+    url = ResolvePossiblyRelativeURL(url_string, GetExtension());
+    if (!url.is_valid()) {
+      error_ = ExtensionErrorUtils::FormatErrorMessage(
+          tabs_keys::kInvalidUrlError, url_string);
+      return false;
+    }
+    if (IsCrashURL(url)) {
+      error_ = tabs_keys::kNoCrashBrowserError;
+      return false;
+    }
+
+    // JavaScript URLs can do the same kinds of things as cross-origin XHR, so
+    // we need to check host permissions before allowing them.
+    if (url.SchemeIs(chrome::kJavaScriptScheme)) {
+      if (!GetExtension()->CanExecuteScriptOnPage(
+          offscreen_tab->contents()->GetURL(), NULL, &error_)) {
+        return false;
+      }
+
+      ExtensionMsg_ExecuteCode_Params params;
+      params.request_id = request_id();
+      params.extension_id = extension_id();
+      params.is_javascript = true;
+      params.code = url.path();
+      params.all_frames = false;
+      params.in_main_world = true;
+
+      RenderViewHost* render_view_host =
+          offscreen_tab->contents()->GetRenderViewHost();
+      render_view_host->Send(
+          new ExtensionMsg_ExecuteCode(render_view_host->routing_id(),
+                                       params));
+
+      Observe(offscreen_tab->contents());
+      AddRef();  // balanced in Observe()
+
+      return true;
+    }
+
+    offscreen_tab->SetURL(url);
+
+    // The URL of a tab contents never actually changes to a JavaScript URL, so
+    // this check only makes sense in other cases.
+    if (!url.SchemeIs(chrome::kJavaScriptScheme))
+      DCHECK_EQ(url.spec(), offscreen_tab->contents()->GetURL().spec());
+  }
+
+  // Width and height
+  if (update_props->HasKey(tabs_keys::kWidthKey) ||
+      update_props->HasKey(tabs_keys::kHeightKey)) {
+    int width;
+    if (update_props->HasKey(tabs_keys::kWidthKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          update_props->GetInteger(tabs_keys::kWidthKey, &width));
+    else
+      offscreen_tab->contents()->GetView()->GetContainerSize().width();
+
+    int height;
+    if (update_props->HasKey(tabs_keys::kHeightKey))
+      EXTENSION_FUNCTION_VALIDATE(
+          update_props->GetInteger(tabs_keys::kHeightKey, &height));
+    else
+      offscreen_tab->contents()->GetView()->GetContainerSize().height();
+
+    offscreen_tab->SetSize(width, height);
+  }
+
+  // Callback
+  if (has_callback()) {
+    result_.reset(offscreen_tab->CreateValue());
+    SendResponse(true);
+  }
+
+  return true;
+}