Allow Mock IME to customize background color

With this CL, background color of the input view of Mock IME can be
customized as follows:

  try(MockImeSession imeSession = MockImeSession.create(
        InstrumentationRegistry.getContext(),
        InstrumentationRegistry.getInstrumentation().getUiAutomation(),
        new ImeSettings.Builder().setBackgroundColor(Color.BLUE)) {

      // Use imeSession to interact with the Mock IME here.

  }

This should be useful for end-to-end tests that rely on screenshots
taken on the device to assert the expected behavior.

Bug: 69845539
Test: atest CtsInputMethodTestCases
Change-Id: I0030d0d816c428dfd07cec2bf62f6f626ea16814
2 files changed