Remove the ChromeClient.h include from RenderLayerCompositor.h

ChromeClient isn't used in RenderLayerCompositor.h at all, so put the
includes where they belong and reduce header dependencies somewhat.

Review URL: https://codereview.chromium.org/351003002

git-svn-id: svn://svn.chromium.org/blink/trunk@176922 bbb929c8-8fbe-4397-9dbb-9b2b20218538