Expand DragStartHelperTest

Add tests for a plain click (mouse/touch) and
multiple buttons pressed (which causes a confusing
ACTION_MOVE that shoudl be handled properly).

Bug: 29570793
Test: android.support.v13.view.DragStartHelperTest
Change-Id: I768e650692f200ce549f3c2ff24d827d6ff918a2
1 file changed