Fix a crash in skia pipeline, which happens if an empty reorder
barrier is inserted at index 0 in a SkiaDisplayList.
Add a unit test that repro the bug (unit test is crashing wihtout
the fix and passing with the fix).
Test: built and ran skia pipeline with angler-eng and run HWUI unit
tests.
Change-Id: I4aded15021c70cc0ae8daa83bbe8ed0e10a41eef
Implement SkiaRecordingCanvas, RenderNodeDrawable, GLFunctorDrawable,
LayerDrawable, StartReorderBarrierDrawable, EndReorderBarrierDrawable.
Move AnimatedRoundRect and AnimatedCircle in a separate file.
All Skia pipeline files are moved in hwui/pipeline/skia folder.
Add unit tests for RenderNodeDrawable, StartReorderBarrierDrawable,
EndReorderBarrierDrawable and SkiaRecordingCanvas.
Test: I tested manually on 6P devices and did run the unit tests.
Change-Id: If2a347bd1fc4689953822294ce5bf98c7f3f57c7
