Delete FrameLoaderClient::didReceiveDocumentData.

It doesn't do anything as of http://src.chromium.org/viewvc/chrome?view=revision&revision=212390

BUG=none

Review URL: https://chromiumcodereview.appspot.com/19755006

git-svn-id: svn://svn.chromium.org/blink/trunk@154677 bbb929c8-8fbe-4397-9dbb-9b2b20218538