Fix deadlock when switching between two GLSurfaceViews

Some devices only support a single active EGL context.

On those devices, when a second activity that uses a GLSurfaceView
is started in the same process, the second activity can potentially
hang in GLSurfaceView.onWindowResize waiting for its GLSurfaceView
render thread to draw a frame. The second activity's render thread
is waiting to acquire an EGL context, but the first activity's render
thread doesn't know it should release the EGL context.

The fix is to detect the potential hang, and ask the first activity's
render thread to release the EGL context.

Change-Id: Ibb342c68772297744c973bcf5010581cd132db67