ANGLE In Use Dialog Box

When ANGLE is enabled for an app, show a dialog box to the user to
indicate that ANGLE is in use.   This is useful because there are
not (or at least shouldn't be) any visual indication that a different
OpenGL driver is in use.

Bug: 120489005
Test: atest CtsAngleIntegrationHostTestCases
Test: Load an app with ANGLE enabled and verify dialog box is shown.
Test: Load an app without ANGLE and verify dialog box is not shown.
Change-Id: I5d667707841458b4ef63c9f4a5bc07e30cb7c786