Introduce V8HiddenValue

- r165735 removed V8HiddenPropertyName and it caused 6% performance regression in Indexed DB tests (https://code.google.com/p/chromium/issues/detail?id=338383)

- This CL essentially reverts r165735, although this CL is not a simple revert (because simple revert is no longer possible) but a revert with a couple of refactoring.

--- Rename V8HiddenPropertyName to V8HiddenValue.
--- Remove unnecessary hidden names from V8HiddenValue.h.
--- Make V8HiddenValue's methods better. Now V8HiddenValue has {get,set,delete}HiddenValue(), which is easy to understand.

- This CL will fix the performance regression in Indexed DB tests.

- In this CL, V8HiddenValue is still using SetHiddenValue/GetHiddenValue. In the next CL, I'll replace them with private names.

BUG=338383

Review URL: https://codereview.chromium.org/188513004

git-svn-id: svn://svn.chromium.org/blink/trunk@168678 bbb929c8-8fbe-4397-9dbb-9b2b20218538
More rebaselines after VS2013

A bunch of off-by-one differences that look reasonable to me.
g-o-m is scaring me again by consolidating with other platforms,
but I assume it knows what it's doing.

R=dpranke@chromium.org
BUG=348800

Review URL: https://codereview.chromium.org/180743025

git-svn-id: svn://svn.chromium.org/blink/trunk@168679 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[CSS Grid Layout] Add layout test for anonymous grid items

Add a layout test to prevent regressions supporting anonymous grid
items.

TEST=fast/css-grid-layout/anonymous-grid-items.html

Review URL: https://codereview.chromium.org/181183005

git-svn-id: svn://svn.chromium.org/blink/trunk@168680 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add tests for font-variant-ligatures: discretionary-ligatures and historical-ligatures

This is now possible to test with recent fonts added to the layout tests.

BUG=

Review URL: https://codereview.chromium.org/186273003

git-svn-id: svn://svn.chromium.org/blink/trunk@168681 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Turn MQ classes into thread safe

Turns the MQ evaluation classes (MediaQuery, MediaQueryExp and MediaQueryEvaluator) to thread safe by switching them from using AtomicStrings to static strings, initialized by Init.

This CL is a split of https://codereview.chromium.org/171383002/

BUG=

Review URL: https://codereview.chromium.org/178803006

git-svn-id: svn://svn.chromium.org/blink/trunk@168682 bbb929c8-8fbe-4397-9dbb-9b2b20218538