Only delete old frames when a new main frame navigation commits

Also, use RVH* to identify frames, not the process id. when we run out of
processes, several unrelated RVHs might share a process.

BUG=136090,139117
TEST=browser_tests:*WebNavigation*, unit_tests:FrameNavigation*

Review URL: https://chromiumcodereview.appspot.com/10835033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149161 0039d316-1c4b-4281-b951-d872f2087c98
6 files changed