Rewire Android WebView's compositor changed signal.

android_webview/native/aw_contents.cc

Index: android_webview/native/aw_contents.cc
diff --git a/android_webview/native/aw_contents.cc b/android_webview/native/aw_contents.cc
index 44738a3edbbff8e4e28ff62fd1072092703f96e1..fb43e96316e4c938901c71a3d0d5ecdb4e18a31e 100644
--- a/android_webview/native/aw_contents.cc
+++ b/android_webview/native/aw_contents.cc
@@ -172,7 +172,8 @@ AwBrowserPermissionRequestDelegate* AwBrowserPermissionRequestDelegate::FromID(
 }
 
 AwContents::AwContents(std::unique_ptr<WebContents> web_contents)
-    : functor_(nullptr),
+    : content::WebContentsObserver(web_contents.get()),
+      functor_(nullptr),
       browser_view_renderer_(
           this,
           BrowserThread::GetMessageLoopProxyForThread(BrowserThread::UI)),
@@ -184,6 +185,15 @@ AwContents::AwContents(std::unique_ptr<WebContents> web_contents)
   web_contents_->SetUserData(android_webview::kAwContentsUserDataKey,
                              new AwContentsUserData(this));
   browser_view_renderer_.RegisterWithWebContents(web_contents_.get());
+
+  CompositorID compositor_id;
+  if (web_contents_->GetRenderProcessHost() &&
+      web_contents_->GetRenderViewHost()) {
+    compositor_id.process_id = web_contents_->GetRenderProcessHost()->GetID();
+    compositor_id.routing_id = web_contents_->GetRoutingID();
+  }
+
+  browser_view_renderer_.SetActiveCompositorID(compositor_id);
   render_view_host_ext_.reset(
       new AwRenderViewHostExt(this, web_contents_.get()));
 
@@ -1288,4 +1298,18 @@ void SetShouldDownloadFavicons(JNIEnv* env,
   g_should_download_favicons = true;
 }
 
+void AwContents::RenderViewHostChanged(content::RenderViewHost* old_host,
+                                       content::RenderViewHost* new_host) {
+  DCHECK(new_host);
+
+  int process_id = new_host->GetProcess()->GetID();
+  int routing_id = new_host->GetRoutingID();
+  // At this point, the current RVH may or may not contain a compositor. So
+  // compositor_ may be nullptr, in which case
+  // BrowserViewRenderer::DidInitializeCompositor() callback is time when the
+  // new compositor is constructed.
+  browser_view_renderer_.SetActiveCompositorID(
+      CompositorID(process_id, routing_id));
+}
+
 }  // namespace android_webview