Move GrInvariantOutput out of GrProcessor and into its own class.

src/effects/gradients/SkGradientShaderPriv.h

Index: src/effects/gradients/SkGradientShaderPriv.h
diff --git a/src/effects/gradients/SkGradientShaderPriv.h b/src/effects/gradients/SkGradientShaderPriv.h
index 15f94d4693f91317e61ca336cea17c83180e87e0..20f8112ecdbce62f920df7fe997879538e45c614 100644
--- a/src/effects/gradients/SkGradientShaderPriv.h
+++ b/src/effects/gradients/SkGradientShaderPriv.h
@@ -303,6 +303,7 @@ static inline int next_dither_toggle16(int toggle) {
 
 class GrFragmentStage;
 class GrBackendProcessorFactory;
+class GrInvariantOutput;
 
 /*
  * The interpretation of the texture matrix depends on the sample mode. The
@@ -375,7 +376,7 @@ protected:
 
     virtual bool onIsEqual(const GrFragmentProcessor&) const SK_OVERRIDE;
 
-    virtual void onComputeInvariantOutput(InvariantOutput* inout) const SK_OVERRIDE;
+    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const SK_OVERRIDE;
 
     const GrCoordTransform& getCoordTransform() const { return fCoordTransform; }