[CSS Grid Layout] Remove legacy WebKitCSSGridLayoutEnabled 
flag from the Layout Tests.

Most of the layout tests come form WebKit codebase before
the fork, so they still have many legacy and unneeded bits.

This patch removes the WebKitCSSGridLayoutEnabled flag 
setting by the testRunner.

BUG=79180

Review URL: https://codereview.chromium.org/180523004

git-svn-id: svn://svn.chromium.org/blink/trunk@168832 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix crash in RespondWithObserver::respondWith

This is the same fix as r166987 for WaitUntilObserver.

No test is added. The upcoming Chromium CL
https://codereview.chromium.org/178343011/ caught
this crash so it will be tested by it.

BUG=342301

Review URL: https://codereview.chromium.org/192603002

git-svn-id: svn://svn.chromium.org/blink/trunk@168833 bbb929c8-8fbe-4397-9dbb-9b2b20218538