Fix menu crash  Made GetActivatableWindow to follow transient_parent if exists.
Fix menu crash
 Made GetActivatableWindow to follow transient_parent if exists.

BUG=103820
TEST=tbd

Review URL: http://codereview.chromium.org/8523020

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@109660 0039d316-1c4b-4281-b951-d872f2087c98

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