Avoid requiring a recalc to update compositing state for iframes

r164013[1] first exposed this issue when it stopped issuing
StyleChangeFromRenderer in some cases.

The solution here is:
1. iframes always generate RenderLayers. This allows the
compositing update to consider the iframe in the same pass.
2. When the compositing update detects a change it requests
a requirements update in the enclosing frame. In the full
compositing update this will happen in the same pass.

[1] https://src.chromium.org/viewvc/blink?revision=164013&view=revision

BUG=332024

Review URL: https://codereview.chromium.org/149653003

git-svn-id: svn://svn.chromium.org/blink/trunk@166807 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: sync Python to r166688 (and clean up special operations+union code)

Python side to:
Update HTMLFormControlsCollection's named getter to behave according to spec
https://codereview.chromium.org/157013006

This also involves lots of cleaning up to special operations and union type code,
making it more generic and avoiding duplication on the Python side.
* Rename collection => imp
* Rename element => result (for union type in/out variables)
* Remove blank lines in nested code

With a bit more cleaning (post-rewrite), special operations can use the
default methods code generation with only minor changes!

BUG=239771
TBR=haraken

Review URL: https://codereview.chromium.org/158663002

git-svn-id: svn://svn.chromium.org/blink/trunk@166808 bbb929c8-8fbe-4397-9dbb-9b2b20218538
V8PerContextDataHolder should know the world associated with the V8PerContextDataHolder

This is one of incremental steps to clean up code about worlds and contexts.

- Currently V8PerContextDataHolder understands its associated world only if the world is an isolated world. This CL makes V8PerContextDataHolder understand its associated world always.

- This CL adds V8PerIsolateData::m_isMainThread and removes V8PerIsolateData::m_workerDOMDataStore.

BUG=339800

Review URL: https://codereview.chromium.org/146693019

git-svn-id: svn://svn.chromium.org/blink/trunk@166809 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: sync Python to r166680

Python side to:
Rename [GarbageCollected] to [WillBeGarbageCollected]
https://codereview.chromium.org/140663011

BUG=239771
R=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/134683007

git-svn-id: svn://svn.chromium.org/blink/trunk@166810 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Pass the status of enable_oilpan when generating the blink_gc_plugin flags.

Change to blink_gc_plugin_flags.sh in https://codereview.chromium.org/156243006/

BUG=334149
R=ager@chromium.org

Review URL: https://codereview.chromium.org/148783004

git-svn-id: svn://svn.chromium.org/blink/trunk@166811 bbb929c8-8fbe-4397-9dbb-9b2b20218538