Implement a ResourceThrottle for URL overriding in Chrome on Android.

chrome/browser/renderer_host/should_ignore_navigation_resource_throttle.cc

+// 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/renderer_host/should_ignore_navigation_resource_throttle.h"
+
+#include "base/callback.h"
+#include "content/browser/renderer_host/resource_request_info_impl.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/render_view_host.h"
+#include "content/public/browser/render_view_host_delegate.h"
+#include "content/public/browser/resource_request_info.h"
+#include "content/public/browser/resource_throttle_controller.h"
+#include "content/public/common/referrer.h"
+#include "net/url_request/url_request.h"
+
+using content::BrowserThread;
+using content::Referrer;
+using content::RenderViewHost;
+using content::RenderViewHostDelegate;
+using content::ResourceRequestInfo;
+
+namespace {
+
+void CheckShouldIgnoreNavigationOnUiThread(
+    int render_process_id,
+    int render_view_id,
+    const GURL& url,
+    const Referrer& referrer,
+    bool is_content_initiated,
+    base::Callback<void(bool)> callback) {
+
+  RenderViewHost* render_view_host =
+      RenderViewHost::FromID(render_process_id, render_view_id);
+  RenderViewHostDelegate* render_view_host_delegate =
+      render_view_host ? render_view_host->GetDelegate() : NULL;
+  bool should_ignore_navigation = false;
+  if (render_view_host_delegate)
+      should_ignore_navigation =
+          render_view_host_delegate->ShouldIgnoreNavigation(
+              render_view_host, url, referrer, is_content_initiated);

[joth, 2012/05/11 15:34:13]

Enclose in {} when it covers more than one physical line.

[mkosiba (inactive), 2012/05/15 14:20:23]

Done.

+
+  BrowserThread::PostTask(
+      BrowserThread::IO,
+      FROM_HERE,
+      base::Bind(callback, should_ignore_navigation));
+}
+
+} // anonymous namespace

[joth, 2012/05/11 15:34:13]

nit: // namespace

[mkosiba (inactive), 2012/05/15 14:20:23]

Done.

+
+ShouldIgnoreNavigationResourceThrottle::ShouldIgnoreNavigationResourceThrottle(
+    net::URLRequest* request) : request_(request) {

[joth, 2012/05/11 15:34:13]

nit: initializer on its own line when the c'tor does not entirely fit on one
line.

[mkosiba (inactive), 2012/05/15 14:20:23]

Done.

[mkosiba (inactive), 2012/05/15 14:20:23]

Done.

+}
+
+ShouldIgnoreNavigationResourceThrottle::
+    ~ShouldIgnoreNavigationResourceThrottle() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+}
+
+void ShouldIgnoreNavigationResourceThrottle::WillStartRequest(bool* defer) {
+  ShouldDeferRequest(request_->url(), defer);
+}
+
+void ShouldIgnoreNavigationResourceThrottle::WillRedirectRequest(
+    const GURL& new_url,
+    bool* defer) {
+  ShouldDeferRequest(new_url, defer);

[joth, 2012/05/11 15:34:13]

nit: ShouldDeferRequest is a slightly open name (sounds like it should return
bool to me).

Is this extra function call really needed at all?

[mkosiba (inactive), 2012/05/15 14:20:23]

Done
I think the extra function makes it a bit cleaner. The alternative is to call
WillRedirectRequest from WillStartRequest which (to me) is like saying
"redirecting is the same as starting a request". With the extra function it
feels more like "on starting and redirecting a request do the same thing".

+}
+
+void ShouldIgnoreNavigationResourceThrottle::ShouldDeferRequest(
+    const GURL& url,
+    bool* defer) {
+  int render_process_id, render_view_id;
+  if (!ResourceRequestInfo::GetRenderViewForRequest(
+        request_,
+        &render_process_id,
+        &render_view_id)) {
+    *defer = false;
+    return;
+  }
+  *defer = true;
+
+  const ResourceRequestInfo* info = ResourceRequestInfo::ForRequest(request_);
+  // The ShouldIngoreNavigationResourceThrottle should only be created for top
+  // level frame requests.
+  DCHECK(info->IsMainFrame());
+  // TODO: Promote has_user_gesture to ResourceRequestInfo?

[joth, 2012/05/11 15:34:13]

TODO(mkosiba). Or word as a 'in future we may want to...' comment if it's not
strictly something needing doing.

+  const bool is_content_initiated =

[joth, 2012/05/11 15:34:13]

nit: chromium style generally shuns const here. I think you can then squish this
down by one line.

[mkosiba (inactive), 2012/05/15 14:20:23]

Done.

+      content::ResourceRequestInfoImpl::ForRequest(
+          request_)->has_user_gesture();
+
+  BrowserThread::PostTask(
+      BrowserThread::UI,
+      FROM_HERE,
+      base::Bind(
+          &CheckShouldIgnoreNavigationOnUiThread,
+          render_process_id,
+          render_view_id,
+          url,
+          Referrer(GURL(request_->referrer()), info->GetReferrerPolicy()),
+          is_content_initiated,
+          base::Bind(&ShouldIgnoreNavigationResourceThrottle::OnResultObtained,
+                     AsWeakPtr())));

[joth, 2012/05/11 15:34:13]

currytastic :)

+}
+
+void ShouldIgnoreNavigationResourceThrottle::OnResultObtained(
+    bool should_ignore_navigation) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  if (should_ignore_navigation)
+    controller()->Cancel();
+  else

[joth, 2012/05/11 15:34:13]

nit: use braces when there's an else

[mkosiba (inactive), 2012/05/15 14:20:23]

Done.

+    controller()->Resume();
+}