Merge DidStartLoading/DidStopLoading imbalance patch to OOP PDF

This merges this CL https://chromereviews.googleplex.com/32997013/ to OOP PDF
and also corrects some minor differences that had arisen in document loading.

BUG=303491

Review URL: https://codereview.chromium.org/333553003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276954 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/pdf/out_of_process_instance.h b/pdf/out_of_process_instance.h
index ada259f..bd70be2 100644
--- a/pdf/out_of_process_instance.h
+++ b/pdf/out_of_process_instance.h
@@ -328,6 +328,11 @@
   // be painted until this is received.
   bool received_viewport_message_;
 
+  // If true, this means we told the RenderView that we're starting a network
+  // request so that it can start the throbber. We will tell it again once the
+  // document finishes loading.
+  bool did_call_start_loading_;
+
   // The callback for receiving the password from the page.
   scoped_ptr<pp::CompletionCallbackWithOutput<pp::Var> > password_callback_;
 };