Merge changes for Chromium 39.0.2171.71.

This is an experiment with using `git merge --log --edit` instead of rebasing for version updates within the same milestone. This preserves the commit history throughout the whole milestone lifetime and allows us to send pull requests that are processed by the bots when updating versions.

This specific PR is very simple, as there has been only one commit to Blink between .62 and .71.