CrOS - Fix file picker not appearing for Import Bookmarks
CrOS - Fix file picker not appearing for Import Bookmarks

The bookmarks manager does not provide an owning window to the file picker, probably because it is an extension itself.  Use the last active browser, rather than trying to find one for the NULL owning window.

BUG=chromium-os:16608
TEST=manual, try bookmark manager > export bookmarks and import bookmarks

Review URL: http://codereview.chromium.org/7258001

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@90436 0039d316-1c4b-4281-b951-d872f2087c98

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