Remove some unused functions in RenderStyle

Trivial patch, found while investigating another issue. This patch
removes resetMargin and resetBorderRadius.

Review URL: https://codereview.chromium.org/337043002

git-svn-id: svn://svn.chromium.org/blink/trunk@176258 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve the compositing reasons when squashing fails

Currently we just report that "no squashing target was found". There
are many reasons why squashing might fail and this message is not very
informative. This cl expands the list of squashing-related compositing
reasons to make diagnosing layer explosions easier.

R=chrishtr@chromium.org
BUG=None

Review URL: https://codereview.chromium.org/331203003

git-svn-id: svn://svn.chromium.org/blink/trunk@176259 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove RenderImage::styleDidChange.

This simply calls its superclass since about four months ago.
https://codereview.chromium.org/129873009/

Review URL: https://codereview.chromium.org/339753002

git-svn-id: svn://svn.chromium.org/blink/trunk@176260 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix for select PopupMenuList appearance in rtl mode with overlay-scrollbar enabled.

The content should take total window width while overlay-scrollbar is enabled. 

BUG=382900

Review URL: https://codereview.chromium.org/333633003

git-svn-id: svn://svn.chromium.org/blink/trunk@176261 bbb929c8-8fbe-4397-9dbb-9b2b20218538