Update VectorDrawables cache at frame start

Draw VectorDrawables in GPU backed surface. Render VD cache
at the beginning of the frame to avoid context switching.

Test: CTS graphics tests pass.
Change-Id: Ia14e0ec4049c3fa87f03547fbda44043bf8dd793
diff --git a/libs/hwui/pipeline/skia/SkiaPipeline.h b/libs/hwui/pipeline/skia/SkiaPipeline.h
index c58fedf..6f5e719 100644
--- a/libs/hwui/pipeline/skia/SkiaPipeline.h
+++ b/libs/hwui/pipeline/skia/SkiaPipeline.h
@@ -49,6 +49,8 @@
             const std::vector< sp<RenderNode> >& nodes, bool opaque, const Rect &contentDrawBounds,
             sk_sp<SkSurface> surface);
 
+    std::vector<VectorDrawableRoot*>* getVectorDrawables() { return &mVectorDrawables; }
+
     static void destroyLayer(RenderNode* node);
 
     static void prepareToDraw(const renderthread::RenderThread& thread, Bitmap* bitmap);
@@ -119,8 +121,18 @@
             const std::vector< sp<RenderNode> >& nodes, const Rect &contentDrawBounds,
             sk_sp<SkSurface>);
 
+    /**
+     *  Render mVectorDrawables into offscreen buffers.
+     */
+    void renderVectorDrawableCache();
+
     TaskManager mTaskManager;
     std::vector<sk_sp<SkImage>> mPinnedImages;
+
+    /**
+     *  populated by prepareTree with dirty VDs
+     */
+    std::vector<VectorDrawableRoot*> mVectorDrawables;
     static float mLightRadius;
     static uint8_t mAmbientShadowAlpha;
     static uint8_t mSpotShadowAlpha;