Revert of Slim Skia down to just one murmur3 implementation.

src/core/SkChecksum.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkChecksum_DEFINED
 #define SkChecksum_DEFINED
 
@@ skipping 18 matching lines @@
         ROTR = 17,
         ROTL = sizeof(uintptr_t) * 8 - ROTR,
         HALFBITS = sizeof(uintptr_t) * 4
     };
 
     static inline uintptr_t Mash(uintptr_t total, uintptr_t value) {
         return ((total >> ROTR) | (total << ROTL)) ^ value;
     }
 
 public:
-    /**
-     * uint32_t -> uint32_t hash, useful for when you're about to trucate this hash but you
-     * suspect its low bits aren't well mixed.
-     *
-     * This is the Murmur3 finalizer.
-     */
-    static uint32_t Mix(uint32_t hash) {
-        hash ^= hash >> 16;
-        hash *= 0x85ebca6b;
-        hash ^= hash >> 13;
-        hash *= 0xc2b2ae35;
-        hash ^= hash >> 16;
-        return hash;
-    }
 
     /**
      * Calculate 32-bit Murmur hash (murmur3).
      * This should take 2-3x longer than SkChecksum::Compute, but is a considerably better hash.
      * See en.wikipedia.org/wiki/MurmurHash.
      *
      *  @param data Memory address of the data block to be processed. Must be 32-bit aligned.
      *  @param size Size of the data block in bytes. Must be a multiple of 4.
      *  @param seed Initial hash seed. (optional)
      *  @return hash result
      */
     static uint32_t Murmur3(const uint32_t* data, size_t bytes, uint32_t seed=0) {
-        SkASSERTF(SkIsAlign4(bytes), "Expected 4-byte multiple, got %zu", bytes);
+        SkASSERT(SkIsAlign4(bytes));
         const size_t words = bytes/4;
 
         uint32_t hash = seed;
         for (size_t i = 0; i < words; i++) {
             uint32_t k = data[i];
             k *= 0xcc9e2d51;
             k = (k << 15) | (k >> 17);
             k *= 0x1b873593;
 
             hash ^= k;
             hash = (hash << 13) | (hash >> 19);
             hash *= 5;
             hash += 0xe6546b64;
         }
         hash ^= bytes;
-        return Mix(hash);
+        hash ^= hash >> 16;
+        hash *= 0x85ebca6b;
+        hash ^= hash >> 13;
+        hash *= 0xc2b2ae35;
+        hash ^= hash >> 16;
+        return hash;
     }
 
     /**
      *  Compute a 32-bit checksum for a given data block
      *
      *  WARNING: this algorithm is tuned for efficiency, not backward/forward
      *  compatibility.  It may change at any time, so a checksum generated with
      *  one version of the Skia code may not match a checksum generated with
      *  a different version of the Skia code.
      *
@@ skipping 43 matching lines @@
          *  define.
          */
         if (8 == sizeof(result)) {
             result ^= result >> HALFBITS;
         }
         return static_cast<uint32_t>(result);
     }
 };
 
 #endif