Add LayoutTest for uncancelable TouchEvents

Now that the necessary EventSender changes have landed in chromium
(https://src.chromium.org/viewvc/chrome?view=rev&revision=265991),
I can more completely test my change for uncancelable TouchEvents
(http://src.chromium.org/viewvc/blink?view=revision&revision=172329).

BUG=365681

Review URL: https://codereview.chromium.org/250843005

git-svn-id: svn://svn.chromium.org/blink/trunk@172689 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused RenderBlock::regionAtBlockOffset()

Review URL: https://codereview.chromium.org/250913002

git-svn-id: svn://svn.chromium.org/blink/trunk@172690 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Introduce ScriptForbiddenScope and guard updateStyle, performLayout and compositing updates

To prevent more cases of script running inside these processes this patch
introduces a scope object that ASSERTS if we try to call into V8 from them.

The only catch is <svg> can initialize the DOMWindow from inside of recalcStyle,
so we also add a special case with AllowScriptForDOMWindowInitialize that
disables the ASSERTS for DOMWindow::initialize. In the future we might make
that async instead.

Note that this scope doesn't use the DocumentLifecycle since not all entry
points to V8 in V8ScriptRunner have access to the ExecutionContext. It also
allows us to put this scope in other places in the code base where lifecycle
might technically allow script execution, but we wish to forbid it for that
function.

Review URL: https://codereview.chromium.org/250803002

git-svn-id: svn://svn.chromium.org/blink/trunk@172691 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Cleanup: removing unused WebExternalTextureLayerClient::context

Review URL: https://codereview.chromium.org/258833003

git-svn-id: svn://svn.chromium.org/blink/trunk@172692 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Disable the HTMLVideoElement-specific prefixed fullscreen API (2nd attempt)

BUG=346236

Review URL: https://codereview.chromium.org/251873002

git-svn-id: svn://svn.chromium.org/blink/trunk@172693 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove ScriptScope

It's no longer used.

BUG=357144
NOTRY=true

Review URL: https://codereview.chromium.org/255783004

git-svn-id: svn://svn.chromium.org/blink/trunk@172694 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove always-false settings for text track selection

Since these settings were not exposed to Chromium or set in any other
way, they were always false. shouldDisplayTextDescriptions was not even
used internally.

While the text track selection needs to be improved, but these settings
made it look like it was more sophisticated than it really is. A new
setting for hard-of-hearing users (preferring captions over subtitles)
may eventually be needed, but that would be a single setting only.

The removed comment no longer makes sense, because the maximum value
returned by textTrackSelectionScore is now the return value of
textTrackLanguageSelectionScore, which is not greater than itself...

BUG=none

Review URL: https://codereview.chromium.org/250923003

git-svn-id: svn://svn.chromium.org/blink/trunk@172695 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[webcrypto] Make it safe to delete WebCryptoResult from any thread.

It used to be that WebCrytoResult had to be deleted from the original Blink thread which created it. This posed a challenge for embedders that wanted to defer the work to a background thread. Since it was possible that by the time the work had completed, the original Blink thread was gone (if it was a WebWorker).

The approach taken in this changelist is to split out the state tied to an ExecutionContext into a separate WeakPtr which deletes itself on request completion, or when the ExecutionContext is destroyed.

BUG=366840,245025

Review URL: https://codereview.chromium.org/253563002

git-svn-id: svn://svn.chromium.org/blink/trunk@172696 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[webcrypto] Add a layout test for wraping/unwrapping AES-CBC keys using AES-KW.

BUG=245025

Review URL: https://codereview.chromium.org/250823005

git-svn-id: svn://svn.chromium.org/blink/trunk@172697 bbb929c8-8fbe-4397-9dbb-9b2b20218538