Fix Blink commit type for subframes after initial about:blank load.

Source/web/WebLocalFrameImpl.cpp

Index: Source/web/WebLocalFrameImpl.cpp
diff --git a/Source/web/WebLocalFrameImpl.cpp b/Source/web/WebLocalFrameImpl.cpp
index ab13d530431e1dd3f53ade03028c7b33ef594a4f..62ff47794c63db87f7ed2e0a2f8e5e9c3e9366e2 100644
--- a/Source/web/WebLocalFrameImpl.cpp
+++ b/Source/web/WebLocalFrameImpl.cpp
@@ -1948,10 +1948,9 @@ void WebLocalFrameImpl::loadJavaScriptURL(const KURL& url)
 
 static void ensureFrameLoaderHasCommitted(FrameLoader& frameLoader)
 {
-    if (frameLoader.stateMachine()->committedFirstRealDocumentLoad())
+    if (frameLoader.stateMachine()->committedMultipleRealLoads())
         return;
-    frameLoader.stateMachine()->advanceTo(frameLoader.client()->backForwardLength() > 1 ?
-        FrameLoaderStateMachine::CommittedMultipleRealLoads : FrameLoaderStateMachine::CommittedFirstRealLoad);
+    frameLoader.stateMachine()->advanceTo(FrameLoaderStateMachine::CommittedMultipleRealLoads);

[Charlie Reis, 2015/06/09 07:14:18]

After looking at how Blink uses these states, I think we might want to always
use CommittedMultipleRealLoads here.

Confusingly, Blink uses CommittedFirstRealLoad for the initial about:blank
document in an iframe.  The check that I've moved from NavigationScheduler
(which dictates whether the next commit creates a new history item or not) uses
CommittedMultipleRealLoads, which is the state you're in after leaving
about:blank, even if you only have 1 item in history (i.e., the real page that
replaced about:blank).

[Nate Chapin, 2015/06/09 18:25:33]

CommittedMultipleRealLoads isn't used for a whole lot, if you have a better way
to do the location.assign() special case, I'm happy to remove it.

[Charlie Reis, 2015/06/11 16:43:48]

Oh, I see; it was introduced in https://codereview.chromium.org/76653002/ in
November 2013.

The part that I found confusing was that the about:blank page counted as
"CommittedFirstRealLoad" (as opposed to something like
DisplayingInitialEmptyDocumentPostCommit, which used to exist but was removed in
https://codereview.chromium.org/22891017 in August 2013).  From the name, I
would have expected the first non-about:blank page to count as the
"CommittedFirstRealLoad."

I'm not terribly concerned about fixing that here, though, now that we seem to
have come to a mostly sane situation.  Ok if we fix this and later consider
improvements to CommittedMultipleRealLoads?

 }
 
 void WebLocalFrameImpl::initializeToReplaceRemoteFrame(WebRemoteFrame* oldWebFrame, const WebString& name, WebSandboxFlags flags)