SkTHash: add checksum include

src/core/SkTHash.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
 #ifndef SkTHash_DEFINED
 #define SkTHash_DEFINED
 
+#include "SkChecksum.h"
 #include "SkTypes.h"
 #include "SkTemplates.h"
 
 // Before trying to use SkTHashTable, look below to see if SkTHashMap or SkTHashSet works for you.
 // They're easier to use, usually perform the same, and have fewer sharp edges.
 
 // T and K are treated as ordinary copyable C++ types.
 // Traits must have:
 //   - static K GetKey(T)
 //   - static uint32_t Hash(K)
@@ skipping 213 matching lines @@
 
 private:
     struct Traits {
         static const T& GetKey(const T& item) { return item; }
         static uint32_t Hash(const T& item) { return HashT(item); }
     };
     SkTHashTable<T, T, Traits> fTable;
 };
 
 #endif//SkTHash_DEFINED