Make XPFragmentBuilder only Builder with access to DstCopy.

src/effects/SkBlurMaskFilter.cpp

Index: src/effects/SkBlurMaskFilter.cpp
diff --git a/src/effects/SkBlurMaskFilter.cpp b/src/effects/SkBlurMaskFilter.cpp
index 1b940fbce3783da955bc54bacdf9e13643beb8db..41f0d8dc7fc6c7933cd95988fc3de2ffcc4d2bd1 100644
--- a/src/effects/SkBlurMaskFilter.cpp
+++ b/src/effects/SkBlurMaskFilter.cpp
@@ -678,7 +678,7 @@ private:
     typedef GrGLFragmentProcessor INHERITED;
 };
 
-void OutputRectBlurProfileLookup(GrGLFPFragmentBuilder* fsBuilder,
+void OutputRectBlurProfileLookup(GrGLFragmentBuilder* fsBuilder,
                                  const GrGLShaderBuilder::TextureSampler& sampler,
                                  const char *output,
                                  const char *profileSize, const char *loc,
@@ -715,7 +715,7 @@ void GrGLRectBlurEffect::emitCode(GrGLFPBuilder* builder,
                                             "profileSize",
                                             &profileSizeName);
 
-    GrGLFPFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
+    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     const char *fragmentPos = fsBuilder->fragmentPosition();
 
     if (inputColor) {
@@ -1060,7 +1060,7 @@ void GrGLRRectBlurEffect::emitCode(GrGLFPBuilder* builder,
                                               "blurRadius",
                                               &blurRadiusName);
 
-    GrGLFPFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
+    GrGLFragmentBuilder* fsBuilder = builder->getFragmentShaderBuilder();
     const char* fragmentPos = fsBuilder->fragmentPosition();
 
     // warp the fragment position to the appropriate part of the 9patch blur texture