Add more specialized fragment builders

src/effects/SkAlphaThresholdFilter.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAlphaThresholdFilter.h"
 #include "SkBitmap.h"
 #include "SkDevice.h"
@@ skipping 146 matching lines @@
 
 void GrGLAlphaThresholdEffect::emitCode(EmitArgs& args) {
     GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;
     fInnerThresholdVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kFloat_GrSLType, kDefault_GrSLPrecision,
                                                     "inner_threshold");
     fOuterThresholdVar = uniformHandler->addUniform(kFragment_GrShaderFlag,
                                                     kFloat_GrSLType, kDefault_GrSLPrecision,
                                                     "outer_threshold");
 
-    GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
+    GrGLSLFPFragmentBuilder* fragBuilder = args.fFragBuilder;
     SkString coords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 0);
     SkString maskCoords2D = fragBuilder->ensureFSCoords2D(args.fCoords, 1);
 
     fragBuilder->codeAppendf("\t\tvec2 coord = %s;\n", coords2D.c_str());
     fragBuilder->codeAppendf("\t\tvec2 mask_coord = %s;\n", maskCoords2D.c_str());
     fragBuilder->codeAppend("\t\tvec4 input_color = ");
     fragBuilder->appendTextureLookup(args.fSamplers[0], "coord");
     fragBuilder->codeAppend(";\n");
     fragBuilder->codeAppend("\t\tvec4 mask_color = ");
     fragBuilder->appendTextureLookup(args.fSamplers[1], "mask_coord");
@@ skipping 219 matching lines @@
 }
 
 #ifndef SK_IGNORE_TO_STRING
 void SkAlphaThresholdFilterImpl::toString(SkString* str) const {
     str->appendf("SkAlphaThresholdImageFilter: (");
     str->appendf("inner: %f outer: %f", fInnerThreshold, fOuterThreshold);
     str->append(")");
 }
 #endif