Create GrGLSLVaryingHandler class for program building

src/gpu/gl/GrGLVaryingHandler.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gl/GrGLVaryingHandler.h"
+
+#include "gl/GrGLGpu.h"
+#include "gl/builders/GrGLProgramBuilder.h"
+
+
+GrGLSLVaryingHandler::SeparableVaryingHandle GrGLVaryingHandler::addSeparableVarying(
+                                                                       const char* name,
+                                                                       GrGLSLVertToFrag* v,
+                                                                       GrSLPrecision fsPrecision) {
+    GrGLProgramBuilder* glPB = (GrGLProgramBuilder*) fProgramBuilder;
+    // This call is not used for non-NVPR backends.
+    SkASSERT(glPB->gpu()->glCaps().shaderCaps()->pathRenderingSupport() &&
+             glPB->fArgs.fPrimitiveProcessor->isPathRendering() &&
+             !glPB->fArgs.fPrimitiveProcessor->willUseGeoShader() &&
+             glPB->fArgs.fPrimitiveProcessor->numAttribs() == 0);
+    this->addVarying(name, v, fsPrecision);
+    SeparableVaryingInfo& varyingInfo = fSeparableVaryingInfos.push_back();
+    varyingInfo.fVariable = fFragInputs.back();
+    varyingInfo.fLocation = fSeparableVaryingInfos.count() - 1;
+    return SeparableVaryingHandle(varyingInfo.fLocation);
+}