Revert 34998, more stabbing in the dark to find a perf regression - Mac: impl...

Revert 34998, more stabbing in the dark to find a perf regression - Mac: implement DnD of URLs onto Omnibox.

(DnD of text coming in another patch.)

BUG=24631
TEST=Select a URL/link/file from somewhere (a link in a browser, a URL in text, a file from the desktop, etc.) and drag it to the Omnibox in a Chromium browser window; the contents of the Omnibox should be selected to indicate that a drop would replace its contents; dropping should navigate to the appropriate location.

Review URL: http://codereview.chromium.org/481012

TBR=viettrungluu@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=35038