[ServiceWorker] Fix RenderFrameImpl::isControlledByServiceWorker()

In current code, we check the main frame's data_source in RenderFrameImpl.
But even if the main frame is not controlled by the ServiceWorker the iframe on it could be controlled by the ServiceWorker.
So we must check their own frame_'s data_source.

BUG=411151

Review URL: https://codereview.chromium.org/609283002

Cr-Commit-Position: refs/heads/master@{#297394}

content/renderer/render_frame_impl.cc

@@ -3181,12 +3181,12 @@ blink::WebScreenOrientationClient*
 bool RenderFrameImpl::isControlledByServiceWorker() {
   // If we're in the middle of committing a load, the data source we need
   // will still be provisional.
-  WebFrame* main_frame = render_view_->webview()->mainFrame();
+  DCHECK(frame_);
   WebDataSource* data_source = NULL;
-  if (main_frame->provisionalDataSource())
-    data_source = main_frame->provisionalDataSource();
+  if (frame_->provisionalDataSource())
+    data_source = frame_->provisionalDataSource();
   else
-    data_source = main_frame->dataSource();
+    data_source = frame_->dataSource();
   ServiceWorkerNetworkProvider* provider =
       ServiceWorkerNetworkProvider::FromDocumentState(
           DocumentState::FromDataSource(data_source));