Remove IsSynchronous API from NavigationHandle.

chrome/browser/extensions/api/web_navigation/web_navigation_api.cc

Index: chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
diff --git a/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc b/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
index c15439bae6a5f3ba61cb5e4f6c807d1dee0754b3..eb1f273e9f0fde8143b38baa35d9a02283a6cba3 100644
--- a/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
+++ b/chrome/browser/extensions/api/web_navigation/web_navigation_api.cc
@@ -269,7 +269,7 @@ void WebNavigationTabObserver::RenderFrameHostChanged(
 
 void WebNavigationTabObserver::DidStartNavigation(
     content::NavigationHandle* navigation_handle) {
-  if (navigation_handle->IsSynchronousNavigation() ||
+  if (navigation_handle->IsSamePage() ||

[Charlie Reis, 2016/09/16 22:23:53]

Is this a desirable behavior change, assuming that it doesn't return early for
about:blank anymore?  Or did you find that IsSynchronousNavigation was false for
about:blank?

[nasko, 2016/09/16 23:38:11]

It doesn't account for about:blank anymore, so that should be 1:1 with the code
before.

[Charlie Reis, 2016/09/16 23:59:15]

Hmm, I don't understand.

Was it the case that IsSynchronousNavigation ever returned true for about:blank?
 (I thought so, but maybe I'm wrong.  I often get this case wrong, because I
know some about:blank navigations go through NavigationScheduler and are thus
async.  I thought there were some sync cases, though-- maybe Daniel knows?)

If so, then WebNavigationTabObserver would have early returned for about:blank. 
After this CL, it won't.  Is that ok?

[nasko, 2016/09/20 23:11:20]

I don't think that was ever the case.
This is why I added explicit tests for that in
NavigationHandleImplBrowserTest::VerifySamePage. It tests a brand new iframe
being added with no src attribute, which should account for the initial blank
page. Also it has a case that it navigates a frame with some session history to
about:blank explicitly, which should cover the other cases.
Since even the initial empty document emits DidStartProvisionalLoad, it should
never have been the case that about:blank would get the
IsSynchronousNavigation() return value to be true.

       !FrameNavigationState::IsValidUrl(navigation_handle->GetURL())) {
     return;
   }