Initial implmentation of AnimatedImageDrawables on the RenderThread.

The current implementation schedules the next frame of the images
to be decoded after the current frame completes but potentially
schedules tasks that will result in a no-op execution if a new
frame is not yet needed.

Test: HwAccelerationTest
Change-Id: I0510cb5a1b801abd651327e924deb586af0306d6
diff --git a/libs/hwui/Android.bp b/libs/hwui/Android.bp
index 7cacaf6..17f9b7c 100644
--- a/libs/hwui/Android.bp
+++ b/libs/hwui/Android.bp
@@ -137,6 +137,7 @@
     whole_static_libs: ["libskia"],
 
     srcs: [
+        "hwui/AnimatedImageDrawable.cpp",
         "hwui/Bitmap.cpp",
         "font/CacheTexture.cpp",
         "font/Font.cpp",