Add more specialized fragment builders

Adds specialized fragment builders for primitive and fragment
processors. Removes fragment-specific functionality from the Xfer
fragment builder.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1709153002

Review URL: https://codereview.chromium.org/1709153002
diff --git a/src/gpu/glsl/GrGLSLPrimitiveProcessor.cpp b/src/gpu/glsl/GrGLSLPrimitiveProcessor.cpp
index c2c4d4e..c19239a 100644
--- a/src/gpu/glsl/GrGLSLPrimitiveProcessor.cpp
+++ b/src/gpu/glsl/GrGLSLPrimitiveProcessor.cpp
@@ -34,7 +34,7 @@
     return combined;
 }
 
-void GrGLSLPrimitiveProcessor::setupUniformColor(GrGLSLFragmentBuilder* fragBuilder,
+void GrGLSLPrimitiveProcessor::setupUniformColor(GrGLSLPPFragmentBuilder* fragBuilder,
                                                  GrGLSLUniformHandler* uniformHandler,
                                                  const char* outputName,
                                                  UniformHandle* colorUniform) {