Remove repaint during layout when updating scrollbars.

This CL fixes up the various places where we invalidate and immediately paint
the scrollbars. (RenderLayerScrollableArea, RenderListBox and FrameView).

This necessitates storing the scrollbar damage information in the scrollable
area and then checking/painting if needed in repaintTree().

BUG=336253

Review URL: https://codereview.chromium.org/148093006

git-svn-id: svn://svn.chromium.org/blink/trunk@166235 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move character-related functions from Font to Character.

Introduce a new class, Character to hold all the fun statics
that deal with various character/codepoint properties of text.

Also add FontPlaftormFeatures class that holds statics that
define features, supported by each platform.

R=ksakamoto@chromium.org,eae
BUG=319475

Review URL: https://codereview.chromium.org/134163008

git-svn-id: svn://svn.chromium.org/blink/trunk@166236 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Reland 166223 "Optimize SaveRegister stubs on arm and a64""

pop always requires a register list, even if it only contains one
registers

TBR=dglazkov@chromium.org
BUG=none

Review URL: https://codereview.chromium.org/151433003

git-svn-id: svn://svn.chromium.org/blink/trunk@166237 bbb929c8-8fbe-4397-9dbb-9b2b20218538