Force input coverage to be only a byte in gpu shaders.

src/gpu/gl/builders/GrGLVertexShaderBuilder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLVertexShaderBuilder.h"
 #include "GrGLProgramBuilder.h"
 #include "GrGLShaderStringBuilder.h"
@@ skipping 39 matching lines @@
     fProgramBuilder->fUniformHandles.fViewMatrixUni =
             fProgramBuilder->addUniform(GrGLProgramBuilder::kVertex_Visibility,
                                         kMat33f_GrSLType,
                                         "ViewM",
                                         &viewMName);
 
     // Transform the position into Skia's device coords.
     this->codeAppendf("vec3 pos3 = %s * vec3(%s, 1);", viewMName, fPositionVar->c_str());
 }
 
+void GrGLVertexBuilder::setupBuiltinVertexAttribute(const char* inName, GrGLSLExpr1* out) {
+    GrGLVertToFrag v(kFloat_GrSLType);
+    fProgramBuilder->addVarying(inName, &v);
+    SkString name(inName);
+    name.prepend("in");
+    this->addAttribute(GrShaderVar(name.c_str(),
+                                   kFloat_GrSLType,
+                                   GrShaderVar::kAttribute_TypeModifier));
+    this->codeAppendf("%s = %s;", v.vsOut(), name.c_str());
+    *out = v.fsIn();
+    fEffectAttribOffset++;
+}
+
 void GrGLVertexBuilder::setupBuiltinVertexAttribute(const char* inName, GrGLSLExpr4* out) {
     GrGLVertToFrag v(kVec4f_GrSLType);
     fProgramBuilder->addVarying(inName, &v);
     SkString name(inName);
     name.prepend("in");
     this->addAttribute(GrShaderVar(name.c_str(),
                                    kVec4f_GrSLType,
                                    GrShaderVar::kAttribute_TypeModifier));
     this->codeAppendf("%s = %s;", v.vsOut(), name.c_str());
     *out = v.fsIn();
@@ skipping 94 matching lines @@
     for (int i = 0; i < fInputs.count(); ++i) {
         const GrGLShaderVar& attr = fInputs[i];
         // if attribute already added, don't add it again
         if (attr.getName().equals(var.getName())) {
             return false;
         }
     }
     fInputs.push_back(var);
     return true;
 }