Implement SkiaRecordingCanvas, RenderNodeDrawable and other drawables.

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
diff --git a/libs/hwui/SkiaCanvas.h b/libs/hwui/SkiaCanvas.h
index d1edff9..a0cdfcb 100644
--- a/libs/hwui/SkiaCanvas.h
+++ b/libs/hwui/SkiaCanvas.h
@@ -40,6 +40,8 @@
      */
     explicit SkiaCanvas(SkCanvas* canvas);
 
+    virtual ~SkiaCanvas();
+
     virtual SkCanvas* asSkCanvas() override {
         return mCanvas.get();
     }