Add transfer size paramater to didFinishLoading [3/3]

Mini DD:
https://docs.google.com/a/chromium.org/document/d/1kAKnBKofLc3Tex_JPveubwJcQLT3BhIL3xNQyjvRIps/edit?usp=sharing

BUG=111052

Review URL: https://codereview.chromium.org/156623005

git-svn-id: svn://svn.chromium.org/blink/trunk@166909 bbb929c8-8fbe-4397-9dbb-9b2b20218538