Implement a module system for the extension bindings JS.

chrome/renderer/extensions/event_bindings.cc

Index: chrome/renderer/extensions/event_bindings.cc
diff --git a/chrome/renderer/extensions/event_bindings.cc b/chrome/renderer/extensions/event_bindings.cc
index 9bab21a945d08f7f2261a6f47c3a2499b18d8a9a..8a425043f5d3ab3bbcca2e0e5ccc3965ed94fd28 100644
--- a/chrome/renderer/extensions/event_bindings.cc
+++ b/chrome/renderer/extensions/event_bindings.cc
@@ -39,24 +39,22 @@ using content::RenderThread;
 
 namespace {
 
+// TODO(koz): Merge this into EventBindings.
 class ExtensionImpl : public ChromeV8Extension {
  public:
-  explicit ExtensionImpl(ExtensionDispatcher* dispatcher)
-      : ChromeV8Extension("extensions/event.js",
-                          IDR_EVENT_BINDINGS_JS,
-                          dispatcher) {
-  }
-  ~ExtensionImpl() {}
+  // A map of event names to the number of contexts listening to that event.
+  // We notify the browser about event listeners when we transition between 0
+  // and 1.
+  typedef std::map<std::string, int> EventListenerCounts;
 
-  virtual v8::Handle<v8::FunctionTemplate> GetNativeFunction(
-      v8::Handle<v8::String> name) {
-    if (name->Equals(v8::String::New("AttachEvent"))) {
-      return v8::FunctionTemplate::New(AttachEvent, v8::External::New(this));
-    } else if (name->Equals(v8::String::New("DetachEvent"))) {
-      return v8::FunctionTemplate::New(DetachEvent, v8::External::New(this));
-    }
-    return ChromeV8Extension::GetNativeFunction(name);
+  ExtensionImpl(ExtensionDispatcher* dispatcher,
+      std::map<std::string, EventListenerCounts>* listener_counts)
+      : ChromeV8Extension(dispatcher),
+        listener_counts_(listener_counts) {
+    RouteStaticFunction("AttachEvent", &AttachEvent);
+    RouteStaticFunction("DetachEvent", &DetachEvent);

[Matt Perry, 2012/02/28 20:34:20]

Both of these access the ExtensionImpl via
GetFromArguments<ExtensionImpl>(args); Would they not need to do so if they
became member functions, and used RouteFunction?

[koz (OOO until 15th September), 2012/03/01 03:41:56]

Yes, that's right. I was planning on making those conversions in a separate
change to reduce the number of delta lines in this one.

   }
+  ~ExtensionImpl() {}
 
   // Attach an event name to an object.
   static v8::Handle<v8::Value> AttachEvent(const v8::Arguments& args) {
@@ -76,7 +74,7 @@ class ExtensionImpl : public ChromeV8Extension {
         return v8::Undefined();
 
       EventListenerCounts& listener_counts =
-          self->listener_counts_[context->extension_id()];
+          (*(self->listener_counts_))[context->extension_id()];
       if (++listener_counts[event_name] == 1) {
         content::RenderThread::Get()->Send(
             new ExtensionHostMsg_AddListener(context->extension_id(),
@@ -110,7 +108,7 @@ class ExtensionImpl : public ChromeV8Extension {
         return v8::Undefined();
 
       EventListenerCounts& listener_counts =
-          self->listener_counts_[context->extension_id()];
+          (*(self->listener_counts_))[context->extension_id()];
       std::string event_name(*v8::String::AsciiValue(args[0]));
       bool is_manual = args[1]->BooleanValue();
 
@@ -135,10 +133,6 @@ class ExtensionImpl : public ChromeV8Extension {
   }
 
  private:
-  // A map of event names to the number of contexts listening to that event.
-  // We notify the browser about event listeners when we transition between 0
-  // and 1.
-  typedef std::map<std::string, int> EventListenerCounts;
 
   bool IsLazyBackgroundPage(const std::string& extension_id) {
     content::RenderView* render_view = GetCurrentRenderView();
@@ -152,13 +146,18 @@ class ExtensionImpl : public ChromeV8Extension {
             helper->view_type() == chrome::VIEW_TYPE_EXTENSION_BACKGROUND_PAGE);
   }
 
-  // A map of extension IDs to listener counts for that extension.
-  std::map<std::string, EventListenerCounts> listener_counts_;
+  std::map<std::string, ExtensionImpl::EventListenerCounts>* listener_counts_;
 };
 
 }  // namespace
 
-v8::Extension* EventBindings::Get(ExtensionDispatcher* dispatcher) {
-  static v8::Extension* extension = new ExtensionImpl(dispatcher);
-  return extension;
+ChromeV8Extension* EventBindings::Get(ExtensionDispatcher* dispatcher) {
+  // A map of extension IDs to listener counts for that extension.
+  static std::map<std::string, ExtensionImpl::EventListenerCounts>*
+      listener_counts = NULL;
+  if (!listener_counts) {
+    listener_counts =
+        new std::map<std::string, ExtensionImpl::EventListenerCounts>();
+  }
+  return new ExtensionImpl(dispatcher, listener_counts);

[Matt Perry, 2012/02/28 20:34:20]

I don't understand this set of changes. Why change the ownership of
listener_counts? It will leak on shutdown. That may anger the memory bots. And
why return a new ExtensionImpl each time instead of caching it in a static var?

[koz (OOO until 15th September), 2012/03/01 03:41:56]

With this change ChromeV8Extensions are no longer singletons, so their state is
now per-context instead of per-process, so to preserve the semantics here
listener_counts_ needs to be shared across all the instances.

I've changed this to use LazyInstance (as per aa's comment elsewhere).

 }