GPU implementation of drawRegion()

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 689 matching lines @@
         @param paint    The paint used to draw the rect
     */
     void drawRectCoords(SkScalar left, SkScalar top, SkScalar right,
                         SkScalar bottom, const SkPaint& paint);
 
     /** Draw the outline of the specified region using the specified paint.
         @param region   The region to be drawn
         @param paint    The paint used to draw the region
     */
     void drawRegion(const SkRegion& region, const SkPaint& paint) {
+        if (region.isEmpty()) {
+            return;
+        }
+
         this->onDrawRegion(region, paint);
     }
 
     /** Draw the specified oval using the specified paint. The oval will be
         filled or framed based on the Style in the paint.
         @param oval     The rectangle bounds of the oval to be drawn
         @param paint    The paint used to draw the oval
     */
     void drawOval(const SkRect& oval, const SkPaint&);
 
@@ skipping 975 matching lines @@
 
 class SkCanvasClipVisitor {
 public:
     virtual ~SkCanvasClipVisitor();
     virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
 };
 
 #endif