Don't explicitly check isRoot in layerTypeRequired.

The document element is always coerced to being a block, so
the check in RenderBoxModelObject is never hit.

The document element also always creates a stacking context,
so the isRoot check in RenderBox is redundant with the hasAutoZIndex
check.

Review URL: https://codereview.chromium.org/224733017

git-svn-id: svn://svn.chromium.org/blink/trunk@170987 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Drop Isolate::GetCurrent() call from V8PerIsolateData

BUG=none
TBR=haraken@chromium.org

Review URL: https://codereview.chromium.org/227733003

git-svn-id: svn://svn.chromium.org/blink/trunk@170988 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Selectively disable rubber banding on mac (part 2).

The logic for handling 2-finger swipes should be:
1. If a 2-finger swipe can scroll the content (or iframe), it should do so.
2. If the 2-finger swipe can cause history navigation, it should do so.
3. The 2-finger swipe should rubber-band the content view.

(2) is handled by the embedder, and (1 & 3) by the renderer. Right now, the
renderer is passed an IPC, and it tries to do (1), and then it tries to do (3).
I've modified the event passed in so that there are flags that prevent the
renderer from performing (3) under specific circumstances.

There was an existing mechanism to determine whether the renderer should try
(3), but it was fragile, incorrectly used, and insufficient for newer features
in chrome - the user can cancel a history swipe without cancelling the gesture,
at which point rubber-banding should be possible again. I've simplified and
fixed the logic inside ScrollElasticityController.mm to reflect the desired
behavior.

This is part 2 of a two-part change. It includes the changes to
ScrollElasticityController to use the new parameters on the WheelEvent. It also
removes references to the old 2 parameter constructor for platformWheelEvent,
in favor of the 4 parameter constructor.

BUG=321437

Review URL: https://codereview.chromium.org/219473003

git-svn-id: svn://svn.chromium.org/blink/trunk@170989 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix missing field initialization in FontPlatformData constructor

Initialize the windows only m_paintTextFlags, m_minSizeForAntiAlias, and
m_useSubpixelPositioning flags in all the FontPlatformData constructors.

R=leviw@chromium.org
BUG=360476

Review URL: https://codereview.chromium.org/227773003

git-svn-id: svn://svn.chromium.org/blink/trunk@170992 bbb929c8-8fbe-4397-9dbb-9b2b20218538