Merge DidStartLoading/DidStopLoading imbalance patch to OOP PDF

This merges this CL https://chromereviews.googleplex.com/32997013/ to OOP PDF
and also corrects some minor differences that had arisen in document loading.

BUG=303491

Review URL: https://codereview.chromium.org/333553003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276954 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed