Optimize CSS box-shadow performance by caching the SkMask of the blur effect.

src/core/SkMaskFilter.cpp

Index: src/core/SkMaskFilter.cpp
diff --git a/src/core/SkMaskFilter.cpp b/src/core/SkMaskFilter.cpp
index 8b9792c2c4fbddf182acb3726586709a34a13693..b8e632d0a3b51563f78af98b252a52fd2334e1cb 100644
--- a/src/core/SkMaskFilter.cpp
+++ b/src/core/SkMaskFilter.cpp
@@ -223,7 +223,6 @@ bool SkMaskFilter::filterRRect(const SkRRect& devRRect, const SkMatrix& matrix,
     }
     draw_nine(patch.fMask, patch.fOuterRect, patch.fCenter, true, clip,
               bounder, blitter);
-    SkMask::FreeImage(patch.fMask.fImage);

[tomhudson, 2014/05/22 10:01:50]

NinePatch doesn't inherit from BlurMaskRecord, so you aren't getting this
deletion from the destructor, right?

[Jun Jiang, 2014/05/23 02:06:28]

Currently NinePatch and BlurMaskRecord are two independent structures. The only
connection is that the SkMask data member in each of them points to the same
Image memory.

Since the idea is to cache the blured SkMask, so the Image memory is only freed
when the BlurMaskRecord is destructed. For NinePatch, it either reuse the cached
Image memory in BlurMaskRecord or generate the Image memory and then cache it in
a BlurMaskRecord, 

     return true;
 }
 
@@ -248,7 +247,6 @@ bool SkMaskFilter::filterPath(const SkPath& devPath, const SkMatrix& matrix,
             case kTrue_FilterReturn:
                 draw_nine(patch.fMask, patch.fOuterRect, patch.fCenter,
                           1 == rectCount, clip, bounder, blitter);
-                SkMask::FreeImage(patch.fMask.fImage);
                 return true;
 
             case kUnimplemented_FilterReturn: