Test onHandleScreenshot for approximate pixel equality to expected view.

Set up mechanism to wait for the third party app to resume fully before
launching assist on it to ensure the view has finished loading.
Screenshot equality tested with solid color views. A percentage of
pixels of that color in the screenshot above a certain threshold passes
the test.

Bug: 21668302

Change-Id: Ibe1826e6ff0ea510e1d5f0d1987947fa303fbe81
21 files changed