Navigation transitions: Added "addStyleSheetByURL" function to insert stylesheet links. 

If transition-entering-stylesheet is defined in the response headers for the incoming document, they're parsed out, passed to the TransitionPageHelper in the embedder, and are applied to the page via addStyleSheetByUrl at the appropriate time in the transition. 

This is the chrome side of the CL, blink side here: https://codereview.chromium.org/285623003/ 

Design doc: https://docs.google.com/a/chromium.org/document/d/17jg1RRL3RI969cLwbKBIcoGDsPwqaEdBxafGNYGwiY4/edit# 
Implementation details: https://docs.google.com/a/chromium.org/document/d/1kREPtFJaeLoDKwrfmrYTD7DHCdxX1RzFBga2gNY8lyE/edit#heading=h.bng2kpmyvxq5 
BUG=370696

Review URL: https://codereview.chromium.org/309143002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278856 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/renderer/render_frame_impl.h b/content/renderer/render_frame_impl.h
index 97cd4eb9..71be416 100644
--- a/content/renderer/render_frame_impl.h
+++ b/content/renderer/render_frame_impl.h
@@ -458,6 +458,7 @@
   void OnExtendSelectionAndDelete(int before, int after);
   void OnReload(bool ignore_cache);
   void OnTextSurroundingSelectionRequest(size_t max_length);
+  void OnAddStyleSheetByURL(const std::string& url);
 #if defined(OS_MACOSX)
   void OnCopyToFindPboard();
 #endif