add virtuals to optimize composing colorfilters

include/effects/SkColorMatrix.h

 /*
  * Copyright 2007 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkColorMatrix_DEFINED
 #define SkColorMatrix_DEFINED
 
@@ skipping 41 matching lines @@
 
     void setSaturation(SkScalar sat);
     void setRGB2YUV();
     void setYUV2RGB();
 
     bool operator==(const SkColorMatrix& other) const {
         return 0 == memcmp(fMat, other.fMat, sizeof(fMat));
     }
 
     bool operator!=(const SkColorMatrix& other) const { return !((*this) == other); }
+
+    static bool NeedsClamping(const SkScalar[20]);
+    static void SetConcat(SkScalar result[20], const SkScalar outer[20], const SkScalar inner[20]);
 };
 
 #endif