PlzNavigate: Allow frames to fallback to alternative content.

third_party/WebKit/public/web/WebLocalFrame.h

Index: third_party/WebKit/public/web/WebLocalFrame.h
diff --git a/third_party/WebKit/public/web/WebLocalFrame.h b/third_party/WebKit/public/web/WebLocalFrame.h
index 3d452f434c421353e633943028ebe7f1a38275e1..effdfe6748abbc28b356d658234104510e17dcb1 100644
--- a/third_party/WebKit/public/web/WebLocalFrame.h
+++ b/third_party/WebKit/public/web/WebLocalFrame.h
@@ -10,6 +10,7 @@
 #include "WebFrameLoadType.h"
 #include "WebHistoryItem.h"
 #include "public/platform/WebCachePolicy.h"
+#include "public/platform/WebURLError.h"
 
 namespace blink {
 
@@ -123,6 +124,13 @@ class WebLocalFrame : public WebFrame {
                         WebHistoryLoadType = WebHistoryDifferentDocumentLoad,
                         bool isClientRedirect = false) = 0;
 
+  // Check if the frame's parent can render fallback content on load failure.
+  virtual bool canRenderFallbackContent() const = 0;

[Nate Chapin, 2016/11/02 17:18:09]

I don't really like having this on the public/ api.

Could we just have:

virtual bool maybeRenderFallbackContent(const WebURLError&)

...so that we don't need both of these functions?

[arthursonzogni, 2016/11/03 15:10:42]

Done.

+
+  // Allow the embedders to report that a navigation they handle has failed. The
+  // frame's parent will display fallback content, if possible.
+  virtual void loadFailed(const WebURLError&) = 0;
+
   // Navigation State -------------------------------------------------------
 
   // Returns true if the current frame's load event has not completed.