Fixing RecordingImageBufferSurface to stay in display list mode

This fix makes RecordingImageBufferSurface track the initial
stack level of the SkPicture recording canvas to avoid falsely
rejecting canvases from display list mode due to state present
on the stack

BUG=396800
TEST=RecordingImageBufferSurfaceTest platform unit tests
NOTRY=true

Review URL: https://codereview.chromium.org/412993004

git-svn-id: svn://svn.chromium.org/blink/trunk@178804 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use isHTMLPlugInElement to replace checks 

All the checked Elements (<object>, <embed>, <applet>) derive from
HTMLPlugInElement and there is no other class deriving from it, so
use isHTMLPlugInElement here instead.

Review URL: https://codereview.chromium.org/413783002

git-svn-id: svn://svn.chromium.org/blink/trunk@178805 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove setting for disabling cc touch hit testing.

Compositor touch hit testing was re-enabled on Android webview back in February
(https://codereview.chromium.org/183943002) and we haven't had any complaints
since. It's probably safe to remove the flag and related code now.

This is part 2 of 2, depends on Chromium CL:
https://codereview.chromium.org/399953004

BUG=304518

Review URL: https://codereview.chromium.org/406053002

git-svn-id: svn://svn.chromium.org/blink/trunk@178806 bbb929c8-8fbe-4397-9dbb-9b2b20218538