Add a force-layout-height-to-zero layout mode to WebViewImpl

This makes it possible for the android_webview to implement
'wrap_content' mode for the view's height without completely ignoring
the viewport meta tag (like it's doing now).

BUG=392460

Review URL: https://codereview.chromium.org/382543003

git-svn-id: svn://svn.chromium.org/blink/trunk@179705 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Clean up testing.internals argument type checking.

Make use of [TypeChecking=Interface] where possible, fixing null pointer
deref over internals.addTextMatchMarker in the process.

R=haraken@chromium.org
BUG=375712

Review URL: https://codereview.chromium.org/445933003

git-svn-id: svn://svn.chromium.org/blink/trunk@179706 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Convert fullscreen pixel tests to reftests

Review URL: https://codereview.chromium.org/451483004

git-svn-id: svn://svn.chromium.org/blink/trunk@179707 bbb929c8-8fbe-4397-9dbb-9b2b20218538