Rename testRunner.dumpAsText(true) to testRunner.dumpAsTextWithPixelResults()

The bool parameter is confusing.

BUG=None
R=pdr@chromium.org

Review URL: https://codereview.chromium.org/24438004

git-svn-id: svn://svn.chromium.org/blink/trunk@158331 bbb929c8-8fbe-4397-9dbb-9b2b20218538