Convert GrClip to an abstract base class

src/core/SkImageFilter.cpp

Index: src/core/SkImageFilter.cpp
diff --git a/src/core/SkImageFilter.cpp b/src/core/SkImageFilter.cpp
index 899083dbb468260a3b63d04b6e5354971f84f34c..761c57bb173628f43531f35cb561a4fb5950e25a 100644
--- a/src/core/SkImageFilter.cpp
+++ b/src/core/SkImageFilter.cpp
@@ -287,13 +287,13 @@ sk_sp<SkSpecialImage> SkImageFilter::DrawWithFP(GrContext* context,
         return nullptr;
     }
 
-    SkRect srcRect = SkRect::Make(bounds);
-    SkRect dstRect = SkRect::MakeWH(srcRect.width(), srcRect.height());
-    GrClip clip(dstRect);
+    const SkIRect& dstIRect = SkIRect::MakeWH(bounds.width(), bounds.height());

[bsalomon, 2016/05/13 02:34:12]

Does the change to references here add any value?

[Chris Dalton, 2016/05/13 03:53:46]

Semantically it avoids a copy constructor. But since these just use the default
copy constructor I would hope a good compiler would optimize that out anyway.

I only changed the two below to bind to the temporaries because I wanted to do
it for devIBounds, and it would have felt inconsistent if those two didn't as
well.

Either way I don't have a strong preference.

[bsalomon, 2016/05/13 13:44:56]

Ok, given that the Make functions are short NVRO-compatible inline functions and
that SkRect has extremely trivial default constructors I had assumed there was
no copying happening. I don't have a strong opinion either, this just stands out
from other uses of these rect factories that assign to local non-refs.

+    const SkRect& srcRect = SkRect::Make(bounds);
+    const SkRect& dstRect = SkRect::MakeWH(srcRect.width(), srcRect.height());
+    GrFixedClip clip(dstIRect);
     drawContext->fillRectToRect(clip, paint, SkMatrix::I(), dstRect, srcRect);
 
-    return SkSpecialImage::MakeFromGpu(SkIRect::MakeWH(bounds.width(), bounds.height()),
-                                       kNeedNewImageUniqueID_SpecialImage,
+    return SkSpecialImage::MakeFromGpu(dstIRect, kNeedNewImageUniqueID_SpecialImage,
                                        drawContext->asTexture());
 }
 #endif