Add a requiresVertexShader method to GrGLEffect

src/gpu/gl/GrGLEffect.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLEffect_DEFINED
 #define GrGLEffect_DEFINED
 
@@ skipping 33 matching lines @@
         // the number of bits in EffectKey available to GenKey
         kEffectKeyBits = GrBackendEffectFactory::kEffectKeyBits,
     };
 
     typedef GrGLShaderBuilder::TextureSamplerArray TextureSamplerArray;
 
     GrGLEffect(const GrBackendEffectFactory&);
 
     virtual ~GrGLEffect();
 
+    /** Called when GrGLProgram is about to create its GrGLShaderBuilder. When possible, effects
+        should handle programs that don't have a vertex shader. But if an effect requires special
+        vertex processing that can't be accomplished with the fixed pipeline, it can override this
+        method and return true to guarantee the GrGLShaderBuilder in emitCode has a VertexBuilder.
+        */
+    virtual bool requiresVertexShader(const GrDrawEffect&) const { return false; }
+
     /** Called when the program stage should insert its code into the shaders. The code in each
         shader will be in its own block ({}) and so locally scoped names will not collide across
         stages.
 
         @param builder      Interface used to emit code in the shaders.
         @param drawEffect   A wrapper on the effect that generated this program stage.
         @param key          The key that was computed by GenKey() from the generating GrEffect.
                             Only the bits indicated by GrBackendEffectFactory::kEffectKeyBits are
                             guaranteed to match the value produced by GenKey();
         @param outputColor  A predefined vec4 in the FS in which the stage should place its output
@@ skipping 26 matching lines @@
     const char* name() const { return fFactory.name(); }
 
     static EffectKey GenTextureKey(const GrDrawEffect&, const GrGLCaps&);
     static EffectKey GenAttribKey(const GrDrawEffect& stage);
 
 protected:
     const GrBackendEffectFactory& fFactory;
 };
 
 #endif