Hook up guest browser plugins to the accessibility tree.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 87b367671c5376b2a05f60ca7bba999c502fadb4..7ff5d88b6bc37deb890dabdbe4d1fa26604a8f85 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -1796,6 +1796,17 @@ void WebContentsImpl::AccessibilityEventReceived(
       WebContentsObserver, observers_, AccessibilityEventReceived(details));
 }
 
+RenderFrameHost* WebContentsImpl::GetGuestByInstanceID(
+    int browser_plugin_instance_id) {
+  BrowserPluginGuestManager* guest_manager =
+      GetBrowserContext()->GetGuestManager();
+  WebContents* guest = guest_manager->GetGuestByInstanceID(
+      this, browser_plugin_instance_id);
+  if (!guest)
+    return NULL;
+  return guest->GetMainFrame();
+}
+
 void WebContentsImpl::OnShowValidationMessage(
     const gfx::Rect& anchor_in_root_view,
     const base::string16& main_text,