This restores the logic removed from SelectionModifierCursorController
in ag/9994946. A quick sequence of "tap", "drag", "tap" events (such
as when quickly scrolling a small input field) should *not* be treated
as a double-tap.
Bug: 158948887
Test: Manual and unit tests
atest FrameworksCoreTests:EditorTouchStateTest
atest FrameworksCoreTests:EditorCursorDragTest
Change-Id: I9fb9cb06b1e208946566a0f70697c62ee7684ca0