Add a requiresVertexShader method to GrGLEffect

src/gpu/gl/GrGLEffectMatrix.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLEffectMatrix.h"
 #include "GrDrawEffect.h"
 #include "GrTexture.h"
@@ skipping 30 matching lines @@
         key |= kIdentity_MatrixType;
     }
     return key;
 }
 
 GrSLType GrGLEffectMatrix::emitCode(GrGLShaderBuilder* builder,
                                     EffectKey key,
                                     SkString* fsCoordName,
                                     SkString* vsCoordName,
                                     const char* suffix) {
+    // TODO: Handle vertexless shaders here before we start enabling them.
     GrGLShaderBuilder::VertexBuilder* vertexBuilder = builder->getVertexBuilder();
     SkASSERT(NULL != vertexBuilder);
 
     GrSLType varyingType = kVoid_GrSLType;
     const char* uniName;
     key &= kKeyMask;
     switch (key & kMatrixTypeKeyMask) {
         case kIdentity_MatrixType:
             fUniType = kVoid_GrSLType;
             varyingType = kVec2f_GrSLType;
@@ skipping 170 matching lines @@
             if (!fPrevMatrix.cheapEqualTo(combined)) {
                 uniformManager.setSkMatrix(fUni, combined);
                 fPrevMatrix = combined;
             }
             break;
         }
         default:
             GrCrash("Unexpected uniform type.");
     }
 }