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 33 matching lines @@
      */
     static uint32_t Mix(uint32_t hash) {
         hash ^= hash >> 16;
         hash *= 0x85ebca6b;
         hash ^= hash >> 13;
         hash *= 0xc2b2ae35;
         hash ^= hash >> 16;
         return hash;
     }
 
-    // Remind compiler that our users will be intentionally violating strict aliasing by casting
-    // their data to const uint32_t*, so don't apply any strict-aliasing-based optimizations.
-    typedef uint32_t SK_ATTRIBUTE(may_alias) FourByteAligned;
-
     /**
      * 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 FourByteAligned* data, size_t bytes, uint32_t seed=0) {
+    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);
         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;
 
@@ skipping 12 matching lines @@
      *  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.
      *
      *  @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.
      *  @return checksum result
      */
-    static uint32_t Compute(const FourByteAligned* data, size_t size) {
+    static uint32_t Compute(const uint32_t* data, size_t size) {
         SkASSERT(SkIsAlign4(size));
 
         /*
          *  We want to let the compiler use 32bit or 64bit addressing and math
          *  so we use uintptr_t as our magic type. This makes the code a little
          *  more obscure (we can't hard-code 32 or 64 anywhere, but have to use
          *  sizeof()).
          */
         uintptr_t result = 0;
         const uintptr_t* ptr = reinterpret_cast<const uintptr_t*>(data);
@@ skipping 27 matching lines @@
          *  define.
          */
         if (8 == sizeof(result)) {
             result ^= result >> HALFBITS;
         }
         return static_cast<uint32_t>(result);
     }
 };
 
 #endif