PlzNavigate: make MHTML iframe load working.

third_party/WebKit/Source/web/LocalFrameClientImpl.h

Index: third_party/WebKit/Source/web/LocalFrameClientImpl.h
diff --git a/third_party/WebKit/Source/web/LocalFrameClientImpl.h b/third_party/WebKit/Source/web/LocalFrameClientImpl.h
index 43bc8445608cc56cb563609c492a0f024a1278eb..e98cbec96b57978422503448cca4564c4b312223 100644
--- a/third_party/WebKit/Source/web/LocalFrameClientImpl.h
+++ b/third_party/WebKit/Source/web/LocalFrameClientImpl.h
@@ -228,6 +228,11 @@ class LocalFrameClientImpl final : public LocalFrameClient {
   bool IsLocalFrameClientImpl() const override { return true; }
   WebDevToolsAgentImpl* DevToolsAgent();
 
+  // An MHTML Archive is a set of resources, including iframes, that is parsed
+  // as a whole. This function tells whether of not an archive exists and should
+  // be used for loading a subframe.
+  bool IsLoadedAsMHTMLArchive() const;
+
   // The WebFrame that owns this object and manages its lifetime. Therefore,
   // the web frame object is guaranteed to exist.
   Member<WebLocalFrameImpl> web_frame_;