PlzNavigate: Allow frames to fallback to alternative content.

third_party/WebKit/Source/web/WebLocalFrameImpl.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 2048 matching lines @@
   frameRequest.setReplacesCurrentItem(replace);
   if (isClientRedirect)
     frameRequest.setClientRedirect(ClientRedirectPolicy::ClientRedirect);
 
   HistoryItem* historyItem = item;
   frame()->loader().load(
       frameRequest, static_cast<FrameLoadType>(webFrameLoadType), historyItem,
       static_cast<HistoryLoadType>(webHistoryLoadType));
 }
 
+bool WebLocalFrameImpl::maybeRenderFallbackContent(
+    const WebURLError& error) const {
+  DCHECK(frame());
+
+  if (!frame()->owner() || !frame()->owner()->canRenderFallbackContent())
+    return false;
+
+  FrameLoader& frameloader = frame()->loader();
+  frameloader.loadFailed(frameloader.documentLoader(), error);
+  return true;
+}
+
 bool WebLocalFrameImpl::isLoading() const {
   if (!frame() || !frame()->document())
     return false;
   return frame()->loader().stateMachine()->isDisplayingInitialEmptyDocument() ||
          frame()->loader().provisionalDocumentLoader() ||
          !frame()->document()->loadEventFinished();
 }
 
 bool WebLocalFrameImpl::
     isFrameDetachedForSpecialOneOffStopTheCrashingHackBug561873() const {
@@ skipping 309 matching lines @@
     feature = UseCounter::ChromeLoadTimesNpnNegotiatedProtocol;
   } else if (metric == "wasAlternateProtocolAvailable") {
     feature = UseCounter::ChromeLoadTimesWasAlternateProtocolAvailable;
   } else if (metric == "connectionInfo") {
     feature = UseCounter::ChromeLoadTimesConnectionInfo;
   }
   UseCounter::count(frame(), feature);
 }
 
 }  // namespace blink