implement drawAtlas natively on gpu-device

samplecode/SampleAtlas.cpp

Index: samplecode/SampleAtlas.cpp
diff --git a/samplecode/SampleAtlas.cpp b/samplecode/SampleAtlas.cpp
index adf3f5e3a4655dc91a140f5fa88bc9410c70ab0c..ed208c3a77a865eb80f8c66d2829711ccf95eedf 100644
--- a/samplecode/SampleAtlas.cpp
+++ b/samplecode/SampleAtlas.cpp
@@ -68,11 +68,13 @@ class DrawAtlasDrawable : public SkDrawable {
                 fVelocity.fX = -fVelocity.fX;
             }
             if (fCenter.fY > bounds.bottom()) {
-                SkASSERT(fVelocity.fY > 0);
-                fVelocity.fY = -fVelocity.fY;
+                if (fVelocity.fY > 0) {
+                    fVelocity.fY = -fVelocity.fY;
+                }
             } else if (fCenter.fY < bounds.top()) {
-                SkASSERT(fVelocity.fY < 0);
-                fVelocity.fY = -fVelocity.fY;
+                if (fVelocity.fY < 0) {
+                    fVelocity.fY = -fVelocity.fY;
+                }
             }
 
             fScale += fDScale;