Add explicit clip to SkSpecialSurface's SkCanvas

src/core/SkSpecialSurface.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file
  */
 
 #include "SkCanvas.h"
 #include "SkSpecialImage.h"
 #include "SkSpecialSurface.h"
@@ skipping 59 matching lines @@
                             SkPixelRef* pr,
                             const SkIRect& subset,
                             const SkSurfaceProps* props)
         : INHERITED(proxy, subset, props) {
         const SkImageInfo& info = pr->info();
 
         fBitmap.setInfo(info, info.minRowBytes());
         fBitmap.setPixelRef(pr);
 
         fCanvas.reset(new SkCanvas(fBitmap, this->props()));
+        fCanvas->clipRect(SkRect::Make(subset));
     }
 
     ~SkSpecialSurface_Raster() override { }
 
     sk_sp<SkSpecialImage> onMakeImageSnapshot() override {
         return SkSpecialImage::MakeFromRaster(this->proxy(), this->subset(), fBitmap,
                                               &this->props());
     }
 
 private:
@@ skipping 37 matching lines @@
 
         SkASSERT(fTexture->asRenderTarget());
 
         SkAutoTUnref<SkGpuDevice> device(SkGpuDevice::Create(fTexture->asRenderTarget(), props,
                                                              SkGpuDevice::kUninit_InitContents));
         if (!device) {
             return;
         }
 
         fCanvas.reset(new SkCanvas(device));
+        fCanvas->clipRect(SkRect::Make(subset));
     }
 
     ~SkSpecialSurface_Gpu() override { }
 
     sk_sp<SkSpecialImage> onMakeImageSnapshot() override {
         return SkSpecialImage::MakeFromGpu(this->proxy(), this->subset(),
                                            kNeedNewImageUniqueID_SpecialImage, fTexture,
                                            &this->props());
     }
 
@@ skipping 42 matching lines @@
 }
 
 sk_sp<SkSpecialSurface> SkSpecialSurface::MakeRenderTarget(SkImageFilter::Proxy* proxy,
                                                            GrContext* context,
                                                            const GrSurfaceDesc& desc,
                                                            const SkSurfaceProps* props) {
     return nullptr;
 }
 
 #endif