Ensure that the pending entry is cleared when a navigation commits.

Ensure that the pending entry is cleared when a navigation commits.

This avoids generating commit events for the wrong entry if the pending
entry differs from the navigation that committed.

BUG=177769
TEST=Go back fast across iframe navigations to the NTP.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=184239

[Charlie Reis, 2013-02-22 21:30:23]

Brett, can you take a look?

https://codereview.chromium.org/12340035/diff/1/content/browser/web_contents/...
File content/browser/web_contents/navigation_controller_impl.cc (right):

https://codereview.chromium.org/12340035/diff/1/content/browser/web_contents/...
content/browser/web_contents/navigation_controller_impl.cc:919:
NavigationEntryImpl::FromNavigationEntry(GetLastCommittedEntry());
This was the source of the bug, since we were using the pending entry before. 
Now it's just to be safe, given that the pending entry is discarded above.

https://codereview.chromium.org/12340035/diff/1/content/browser/web_contents/...
content/browser/web_contents/navigation_controller_impl.cc:930:
CHECK(active_entry->site_instance() == web_contents_->GetSiteInstance());
This DCHECK would have caught the bug, so I'd like to promote it to a CHECK so
that we have crash dumps to help diagnose it if it happens again.

[brettw, 2013-02-22 21:37:40]

lgtm

[commit-bot: I haz the power, 2013-02-22 21:51:08]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/creis@chromium.org/12340035/1

[Charlie Reis, 2013-02-23 00:58:30]

Committed patchset #1 manually as r184239 (presubmit successful).