SkTDynamicHash: pick up GetKey(), Hash() from T by default.

src/core/SkTDynamicHash.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTDynamicHash_DEFINED
 #define SkTDynamicHash_DEFINED
 
 #include "SkMath.h"
 #include "SkTemplates.h"
 #include "SkTypes.h"
 
+// Traits requires:
+//   static const Key& GetKey(const T&) { ... }
+//   static uint32_t Hash(const Key&) { ... }
+// We'll look on T for these by default, or you can pass a custom Traits type.
 template <typename T,
           typename Key,
-          const Key& (GetKey)(const T&),
-          uint32_t (Hash)(const Key&),
+          typename Traits = T,
           int kGrowPercent = 75>  // Larger -> more memory efficient, but slower.
 class SkTDynamicHash {
 public:
     SkTDynamicHash() : fCount(0), fDeleted(0), fCapacity(0), fArray(NULL) {
         SkASSERT(this->validate());
     }
 
     ~SkTDynamicHash() {
         sk_free(fArray);
     }
@@ skipping 191 matching lines @@
     int firstIndex(const Key& key) const {
         return Hash(key) & this->hashMask();
     }
 
     // Given index at round N, what is the index to check at N+1?  round should start at 0.
     int nextIndex(int index, int round) const {
         // This will search a power-of-two array fully without repeating an index.
         return (index + round + 1) & this->hashMask();
     }
 
+    static const Key& GetKey(const T& t) { return Traits::GetKey(t); }
+    static uint32_t Hash(const Key& key) { return Traits::Hash(key); }
+
     int fCount;     // Number of non Empty(), non Deleted() entries in fArray.
     int fDeleted;   // Number of Deleted() entries in fArray.
     int fCapacity;  // Number of entries in fArray.  Always a power of 2.
     T** fArray;
 };
 
 #endif