Changed GL enums from GraphicsContext3D to standard versions (Take 2)

Updated all callers to use the standard GL enums. This is the first step in eventually
removing our dependence on GraphicsContext3D's thin WebGraphicsContext3D wrapper.

BUG=326382
TBR=kbr@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/106503003

git-svn-id: svn://svn.chromium.org/blink/trunk@163735 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Removed duplication between logical and physical scroll paths.

Merged logical scroll path into main physical scroll. Made the logical
scroll directions part of the normal ScrollDirection enum and apply
transformation into physical direction if needed at scroll-time.

BUG=325554

Review URL: https://codereview.chromium.org/110803004

git-svn-id: svn://svn.chromium.org/blink/trunk@163736 bbb929c8-8fbe-4397-9dbb-9b2b20218538