Use const access to snapshot from OpenGLRenderer

Additionally, move clipping methods to StatefulBaseRenderer

Change-Id: Iff232bf16fc1ad3b7d89493da6d8915db7bc5e4f
diff --git a/libs/hwui/PathTessellator.h b/libs/hwui/PathTessellator.h
index 236658d..24f20bc 100644
--- a/libs/hwui/PathTessellator.h
+++ b/libs/hwui/PathTessellator.h
@@ -32,13 +32,13 @@
     static void expandBoundsForStroke(SkRect& bounds, const SkPaint* paint);
 
     static void tessellatePath(const SkPath& path, const SkPaint* paint,
-            const mat4 *transform, VertexBuffer& vertexBuffer);
+            const mat4& transform, VertexBuffer& vertexBuffer);
 
     static void tessellatePoints(const float* points, int count, SkPaint* paint,
-            const mat4* transform, SkRect& bounds, VertexBuffer& vertexBuffer);
+            const mat4& transform, SkRect& bounds, VertexBuffer& vertexBuffer);
 
     static void tessellateLines(const float* points, int count, SkPaint* paint,
-            const mat4* transform, SkRect& bounds, VertexBuffer& vertexBuffer);
+            const mat4& transform, SkRect& bounds, VertexBuffer& vertexBuffer);
 
 private:
     static bool approximatePathOutlineVertices(const SkPath &path, bool forceClose,