the parse API in CSSStyleValue should only be exposed to Window

Could you please add some more context to this bug, e.g. a spec link?

meade@: I had an offline discussion with Ian, and he pointed out that the change to the spec is not started yet, but there are discussion over here:
https://github.com/w3c/css-houdini-drafts/issues/237
https://github.com/w3c/css-houdini-drafts/issues/238

Brief summary:
1. We'd like to expose a minimal subset of TypedOM APIs with paint.
2. Constructor and parse method should not be exposed to Window.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7cfabf53936f5b164ba59122bc2e1039931a9003

commit 7cfabf53936f5b164ba59122bc2e1039931a9003
Author: Xida Chen <xidachen@chromium.org>
Date: Fri Jun 09 15:39:37 2017

Change exposure for CSSStyleValue and StylePropertyMapReadOnly

This CL makes CSSStyleValue and StylePropertyMapReadOnly to be exposed to
CSSTypedOM on Window, and CSSPaintAPI on PaintWorklet. It also restricts the
parse API in CSSStyleValue to be exposed to Window only.

The discussion for the change to CSSStyleValue and StylePropertyMapReadOnly
is here: https://github.com/w3c/css-houdini-drafts/issues/237.
The discussion for keep the parse API exposed to Window only is here:
https://github.com/w3c/css-houdini-drafts/issues/238

Bug:  728597 
Change-Id: I489571047829997e5a523f03a4861dbb9737d914
Reviewed-on: https://chromium-review.googlesource.com/521945
Commit-Queue: Xida Chen <xidachen@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Eddy Mead <meade@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#478289}
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/LayoutTests/http/tests/worklet/webexposed/global-interface-listing-paint-worklet-expected.txt
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSKeywordValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSNumericValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSPositionValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSResourceValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSStyleValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSTransformValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/CSSUnparsedValue.idl
[modify] https://crrev.com/7cfabf53936f5b164ba59122bc2e1039931a9003/third_party/WebKit/Source/core/css/cssom/StylePropertyMapReadonly.idl