Add a requiresVertexShader method to GrGLEffect

src/gpu/gl/GrGLEffect.h

Index: src/gpu/gl/GrGLEffect.h
diff --git a/src/gpu/gl/GrGLEffect.h b/src/gpu/gl/GrGLEffect.h
index 5df22811c4c60dfef25794d2294ad49117a60a05..2d7258e026ec76727f935847a01d05a1239f5af5 100644
--- a/src/gpu/gl/GrGLEffect.h
+++ b/src/gpu/gl/GrGLEffect.h
@@ -51,6 +51,13 @@ public:
 
     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.