Fix CoreGraphics and Core Animation drawing for QuickTime plugin

Conditionalizes a SetWindow call that was added to fix a crash in QuickDraw mode, but isn't necessary (and causes QuickTime not to draw) in other drawing modes.

BUG=38336,36896,35081
TEST=Play QuickTime movies on 10.6. The ones with floating controllers (36896) should draw again, and the other should not only work, but have smoother playback and use less CPU. The test case for bug 35081 should still not crash.

Review URL: http://codereview.chromium.org/1569005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@43078 0039d316-1c4b-4281-b951-d872f2087c98