Fixes crash in tab dragging. The crash could occur because we were triggering a nested call to ContinueDragging. Specifically when we went to cancel the nested loop we would invoke ReleaseMouseCapture, which called back to ContinueDragging. I'm avoiding that by removing the observer before doing releasing capture.
Fixes crash in tab dragging. The crash could occur because we were
triggering a nested call to ContinueDragging. Specifically when we
went to cancel the nested loop we would invoke ReleaseMouseCapture,
which called back to ContinueDragging. I'm avoiding that by removing
the observer before doing releasing capture.

BUG=119541
TEST=none
R=ben@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9808042

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@128502 0039d316-1c4b-4281-b951-d872f2087c98

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