Mac: Fix window shadow when compositor is active.
Mac: Fix window shadow when compositor is active.

BUG=53382
TEST=Enable compositor. Window shadow should look normal, even after resizing the window. The shadow of other windows (prefs, bubbles, etc) should look like it did before.

Review URL: http://codereview.chromium.org/3360014

git-svn-id: http://src.chromium.org/svn/trunk/src@58770 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 14f60e3b2d714cd19a130643bb939015e973582e
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser