Remove GP from drawstate, revision of invariant output for GP

include/gpu/GrXferProcessor.h

Index: include/gpu/GrXferProcessor.h
diff --git a/include/gpu/GrXferProcessor.h b/include/gpu/GrXferProcessor.h
index 696359b8b3fb351438c3d0b816e802a23422725f..db0d6e8656c14ae011ca16f9d26f4164a6d1a64c 100644
--- a/include/gpu/GrXferProcessor.h
+++ b/include/gpu/GrXferProcessor.h
@@ -134,6 +134,11 @@ protected:
      */
     void setWillReadDstColor() { fWillReadDstColor = true; }
 
+    /**
+     * Subclass implements this to support getConstantColorComponents(...).
+     */
+    virtual void onComputeInvariantOutput(GrInvariantOutput* inout) const = 0;
+
 private:
     virtual bool onIsEqual(const GrXferProcessor&) const = 0;