add more checks for computing clamp counts, remove dead code

src/effects/gradients/SkClampRange.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkClampRange_DEFINED
 #define SkClampRange_DEFINED
 
@@ skipping 17 matching lines @@
 struct SkClampRange {
     int fCount0;    // count for fV0
     int fCount1;    // count for interpolating (fV0...fV1)
     int fCount2;    // count for fV1
     SkGradFixed fFx1;   // initial fx value for the fCount1 range.
                     // only valid if fCount1 > 0
     int fV0, fV1;
 
     void init(SkGradFixed fx, SkGradFixed dx, int count, int v0, int v1);
 
+    void validate(int count) const {
+#ifdef SK_DEBUG
+        SkASSERT(fCount0 >= 0);
+        SkASSERT(fCount1 >= 0);
+        SkASSERT(fCount2 >= 0);
+        SkASSERT(fCount0 + fCount1 + fCount2 == count);
+#endif
+    }
+
 private:
     void initFor1(SkGradFixed fx);
 };
 
 #endif