When DWM compositing is disabled (i.e. XP, RDP) ensure that windowed NPAPI plugins don't cover UI dialogs. This includes things like omnibox, star window, profile selector, and bookmark editor.

      The solution is to start watching the root window as well as the parent window.
BUG=299224
R=ben@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=234708

Review URL: https://codereview.chromium.org/69833002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234823 0039d316-1c4b-4281-b951-d872f2087c98