Notable changes:
- Merges TwoFingerDragHandler and ToplevelWindowEventHandler
    This fixes crashes due to:
  --- The existence of multiple WindowResizers
  --- Display configuration changes during a two finger drag
- Properly ends window dragging once the third finger is placed on screen.
- Fixes crash as a result of accidentally right clicking during a mouse drag
- Removes DetachToBrowserTabDragControllerTestTouch.DetachToOwnWindowTwoFingers and replaces the test with a new test
  - It used to be the case that putting a second finger down during a tab drag would have no effect but putting a third finger down would revert the drag. Now putting a second and third finger down during a a tab drag revert the drag. This seems to be the intended behavior based on https://chromiumcodereview.appspot.com/10543061

BUG=324038
TEST=Manual, see bug

Review URL: https://codereview.chromium.org/99923011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@247258 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 247258