Merge 73838 - Fix frame accurate seeking for the third time.

Turns out we need to do an integer round to paper over floating point issues.

Refer to discussion on https://bugs.webkit.org/show_bug.cgi?id=52697 for details.

BUG=69499
TEST=layout test in linked bug

Review URL: http://codereview.chromium.org/6250137

TBR=scherkus@chromium.org

git-svn-id: svn://svn.chromium.org/chrome/branches/648/src@75054 0039d316-1c4b-4281-b951-d872f2087c98