Stop disabling force_compositing_mode for background RenderViews.

chrome/browser/tab_contents/background_contents.cc

Index: chrome/browser/tab_contents/background_contents.cc
diff --git a/chrome/browser/tab_contents/background_contents.cc b/chrome/browser/tab_contents/background_contents.cc
index 9420402e6614422bbd1554fc05fd12a153e800c5..ad0ce6281bc403d8b26b2f7ae2faacaa83a44a11 100644
--- a/chrome/browser/tab_contents/background_contents.cc
+++ b/chrome/browser/tab_contents/background_contents.cc
@@ -33,6 +33,7 @@ BackgroundContents::BackgroundContents(
       site_instance->GetBrowserContext());
 
   WebContents::CreateParams create_params(profile_, site_instance);
+  create_params.initially_hidden = true;
   create_params.routing_id = routing_id;
   if (session_storage_namespace) {
     content::SessionStorageNamespaceMap session_storage_namespace_map;
@@ -123,6 +124,13 @@ void BackgroundContents::AddNewContents(WebContents* source,
       new_contents, disposition, initial_pos, user_gesture, was_blocked);
 }
 
+bool BackgroundContents::IsWebContentsNeverVisible(
+    content::WebContents* web_contents) {
+  DCHECK_EQ(extensions::VIEW_TYPE_BACKGROUND_CONTENTS,
+            extensions::GetViewType(web_contents));

[jam, 2014/04/14 22:43:01]

this seems like a redundant dcheck. i would prefer we take it out. i.e. if we
can't trust that random code isn't changing the view type of webcontents in
chrome, then all hope is lost.

[danakj, 2014/04/14 22:47:30]

To me it's not so much about trust but to document the expectations of this
function and why it can return true, in a way that will have to be updated if
things changed in the future. I'd prefer to keep it if you don't feel strongly
about removing it.

+  return true;
+}
+
 void BackgroundContents::RenderProcessGone(base::TerminationStatus status) {
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_BACKGROUND_CONTENTS_TERMINATED,