Avoids releasing pointer grab prematurely
BUG=338247
TEST=
1.Launch chrome://settings..ctrl+D,save the Bookmark in Bookmark Bar.
2.Open 3 to 4 new Tabs via ctrl+T,in chrome://settings page Drag the Bookmark from the Bookmark Bar.
3.Hover the Dragged Bookmark over the second New-Tab and Release the Bookmark over the New-Tab.
4.Hover the Dragged Bookmark over the third New-Tab (the tab gets activated) and Release the Bookmark over the New-Tab.
5.Close browser - should not crash.
Review URL: https://codereview.chromium.org/
140663013
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252201 0039d316-1c4b-4281-b951-d872f2087c98