Convert search for most visible page in the document to a binary search.

The PDF extension needs to compute the most visible page frequently so we use
a binary search.

BUG=303491
R=arv@chromium.org, koz@chromium.org

Review URL: https://codereview.chromium.org/170163003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252177 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252177