[Mac] Fix "Pressing ESC does not cancel in-progress tab drag"	
[Mac] Fix "Pressing ESC does not cancel in-progress tab drag"	

This matches Chrome's behavior on Windows and corresponds to how users expect a drag to behave.

BUG=78437
TEST=1. Start a tab drag within the tab-strip without detaching. Press ESC. Tab should revert to its original position. 2. Start a tab drag that detaches the tab from a window that has multiple tabs. Press ESC. Tab should revert to its original location in its previous window. 3. Start a tab drag of a tab from a single-tab window. Press ESC. The drag should be reverted.

Review URL: http://codereview.chromium.org/6840032

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@81592 0039d316-1c4b-4281-b951-d872f2087c98

adobe/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,yitian134/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,adobe/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,Crystalnix/house-of-life-chromium,ropik/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,adobe/chromium,ropik/chromium,Crystalnix/house-of-life-chromium,Crystalnix/house-of-life-chromium,ropik/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,yitian134/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium,adobe/chromium,ropik/chromium,adobe/chromium,gavinp/chromium,Crystalnix/house-of-life-chromium,gavinp/chromium