PartitionAlloc: Introduce an explicit "recommit" operation.

Previously, recommit was implicit. Now it is an explicit API. The recommit is
currently a no-op on all platforms, but this rearrangement will allow us to
experiment with different commit strategies, particularly on Windows. We're
currently using an uncommon decommit API on Windows, which may be related to
the referenced bug.

BUG=343657

Review URL: https://codereview.chromium.org/271683005

git-svn-id: svn://svn.chromium.org/blink/trunk@174046 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Prevent direct use of "replacement" text encoding.

The "replacement" encoding defined in the WHATWG Encoding Standard
is a spec convenience, and not intended to be referenced directly.
There are several aliases for it (for some legacy encodings) but
neither content nor script should be able to use it by name.

Since most of wtf/text assumes that a codec's name is an alias for
itself, leave that invariant intact. Make TextEncoding (the API
for resolving an encoding by name) mark a direct reference as invalid,
(treating it as any other unknown string, i.e. use locale's default
codec) and throw if the name is used from script (per spec)

This is dependent on http://crrev.com/265973003

BUG=277037
R=jshin@chromium.org,eseidel@chromium.org

Review URL: https://codereview.chromium.org/261013007

git-svn-id: svn://svn.chromium.org/blink/trunk@174047 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Enable clip-path on composited overflow scrolling.

Currently clip-path is pretty broken on accelerated overflow divs,
causing invalidation issues, and preventing the background and
scrollbars from being clipped. This CL should fix all these
issues, except that in some cases scroll children may still
escape outside of the clip (see crbug.com/365828).

BUG=367165

Review URL: https://codereview.chromium.org/283953003

git-svn-id: svn://svn.chromium.org/blink/trunk@174048 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make all layout tests force composited

BUG=361729

Review URL: https://codereview.chromium.org/261143003

git-svn-id: svn://svn.chromium.org/blink/trunk@174049 bbb929c8-8fbe-4397-9dbb-9b2b20218538