PartitionAlloc: wait just a little while before actually freeing empty pages.

We hold a small ring-list cache of recently-emptied pages, and only free the
oldest entry in the ring list when the cache is full. This makes us hold on to
a little bit of unused memory, but in return we do now eventually free the last
slot span in any given bucket, which would have been held indefinitely before.

This patch is a sufficient generic replacement for the bandaid added in
https://code.google.com/p/chromium/issues/detail?id=330798; accordingly, the
bandaid is removed. In fact, we now seem to be +4% faster than _before_ the
original regression.

BUG=332282

Review URL: https://codereview.chromium.org/133863006

git-svn-id: svn://svn.chromium.org/blink/trunk@165112 bbb929c8-8fbe-4397-9dbb-9b2b20218538
AX: remove unused AXObject::selectedText.

This CL removes the followings:
 - AXObject::selectedText
 - AXRenderObject::selectedText, which is an override of AXObject::selectedText
 - AXRenderObject::stringForRange and HTMLTextFormControlElement::selectedText,
   which are used only by AXRenderObject::selectedText.

BUG=none
TEST=none; no behavior changes

Review URL: https://codereview.chromium.org/137783006

git-svn-id: svn://svn.chromium.org/blink/trunk@165113 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move dispatchChangeEvent to HTMLFormControlElement

Also devirtualize it along with dispatchInputEvent.

Based on http://trac.webkit.org/changeset/150805 by Andreas Kling.

Review URL: https://codereview.chromium.org/138003005

git-svn-id: svn://svn.chromium.org/blink/trunk@165114 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Break HarfBuzzShaper::collectHarfBuzzRuns apart

Break out the handling of GC_M_MASK (multiple uchar category) into
separate inline function as a part of the effort to clean up the
logic to allow proper handling of script_common.

BUG=311372
R=leviw@chromium.org

Review URL: https://codereview.chromium.org/138553003

git-svn-id: svn://svn.chromium.org/blink/trunk@165115 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove SVGPathElement::createRenderer

The same functionality is already in SVGGraphicsElement.

Review URL: https://codereview.chromium.org/138923003

git-svn-id: svn://svn.chromium.org/blink/trunk@165116 bbb929c8-8fbe-4397-9dbb-9b2b20218538