Revert of Revert of allow canvas to force conservative clips (for speed)

include/utils/SkNoSaveLayerCanvas.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkNoSaveLayerCanvas_DEFINED
 #define SkNoSaveLayerCanvas_DEFINED
 
 #include "SkCanvas.h"
 #include "SkRRect.h"
 
 // The NoSaveLayerCanvas is used to play back SkPictures when the saveLayer
 // functionality isn't required (e.g., during analysis of the draw calls).
 // It also simplifies the clipping calls to only use rectangles.
 class SK_API SkNoSaveLayerCanvas : public SkCanvas {
 public:
-    SkNoSaveLayerCanvas(SkBaseDevice* device) : INHERITED(device) {}
+    SkNoSaveLayerCanvas(SkBaseDevice* device) : INHERITED(device, kConservativeRasterClip_InitFlag)
+    {}
 
 protected:
     virtual SaveLayerStrategy willSaveLayer(const SkRect* bounds, const SkPaint* paint,
                                             SaveFlags flags) SK_OVERRIDE {
         this->INHERITED::willSaveLayer(bounds, paint, flags);
         return kNoLayer_SaveLayerStrategy;
     }
 
-    // disable aa for speed
-    virtual void onClipRect(const SkRect& rect, SkRegion::Op op, ClipEdgeStyle) SK_OVERRIDE {
-        this->INHERITED::onClipRect(rect, op, kHard_ClipEdgeStyle);
-    }
-
-    // for speed, just respect the bounds, and disable AA. May give us a few
-    // false positives and negatives.
-    virtual void onClipPath(const SkPath& path, SkRegion::Op op, ClipEdgeStyle) SK_OVERRIDE {
-        this->updateClipConservativelyUsingBounds(path.getBounds(), op,
-                                                  path.isInverseFillType());
-    }
-    virtual void onClipRRect(const SkRRect& rrect, SkRegion::Op op, ClipEdgeStyle) SK_OVERRIDE {
-        this->updateClipConservativelyUsingBounds(rrect.getBounds(), op, false);
-    }
-
 private:
     typedef SkCanvas INHERITED;
 };
 
 #endif // SkNoSaveLayerCanvas_DEFINED