Mark cancel-image-via-src-change.html as flaky on debug

Fails in debug with text differerences.

BUG=255183
TBR=dongseong.hwang@intel.com

Review URL: https://codereview.chromium.org/18114007

git-svn-id: svn://svn.chromium.org/blink/trunk@153175 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Re-land http://src.chromium.org/viewvc/blink?revision=153162&view=revision

This time with less "make every test ASSERT".

Migrate most callers of String::characters() to bloatedcharacters()

This CL changes the lion's share of callers from using String::characterrs() to
using String::bloatedCharacters(). This CL makes it easier for us to find these
callers and burn them down.

TBR=esprehn

Review URL: https://codereview.chromium.org/18034013

git-svn-id: svn://svn.chromium.org/blink/trunk@153176 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Gardening: Mark radio-focus-by-mouse-then-keydown.html as flaky on mac

BUG=254332
TBR=tkent@chromium.org

Review URL: https://codereview.chromium.org/18023009

git-svn-id: svn://svn.chromium.org/blink/trunk@153177 bbb929c8-8fbe-4397-9dbb-9b2b20218538