Revert of Slim Skia down to just one murmur3 implementation.

src/core/SkScaledImageCache.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#include "SkChecksum.h"
 #include "SkScaledImageCache.h"
 #include "SkMipMap.h"
 #include "SkPixelRef.h"
 #include "SkRect.h"
 
 // This can be defined by the caller's build system
 //#define SK_USE_DISCARDABLE_SCALEDIMAGECACHE
 
 #ifndef SK_DISCARDABLEMEMORY_SCALEDIMAGECACHE_COUNT_LIMIT
 #   define SK_DISCARDABLEMEMORY_SCALEDIMAGECACHE_COUNT_LIMIT   1024
 #endif
 
 #ifndef SK_DEFAULT_IMAGE_CACHE_LIMIT
     #define SK_DEFAULT_IMAGE_CACHE_LIMIT     (2 * 1024 * 1024)
 #endif
 
 static inline SkScaledImageCache::ID* rec_to_id(SkScaledImageCache::Rec* rec) {
     return reinterpret_cast<SkScaledImageCache::ID*>(rec);
 }
 
 static inline SkScaledImageCache::Rec* id_to_rec(SkScaledImageCache::ID* id) {
     return reinterpret_cast<SkScaledImageCache::Rec*>(id);
 }
 
+ // Implemented from en.wikipedia.org/wiki/MurmurHash.
+static uint32_t compute_hash(const uint32_t data[], int count) {
+    uint32_t hash = 0;
+
+    for (int i = 0; i < count; ++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 ^= size;
+    hash ^= hash >> 16;
+    hash *= 0x85ebca6b;
+    hash ^= hash >> 13;
+    hash *= 0xc2b2ae35;
+    hash ^= hash >> 16;
+
+    return hash;
+}
+
 struct SkScaledImageCache::Key {
     Key(uint32_t genID,
         SkScalar scaleX,
         SkScalar scaleY,
         SkIRect  bounds)
         : fGenID(genID)
         , fScaleX(scaleX)
         , fScaleY(scaleY)
         , fBounds(bounds) {
-        fHash = SkChecksum::Murmur3(&fGenID, 28);
+        fHash = compute_hash(&fGenID, 7);
     }
 
     bool operator<(const Key& other) const {
         const uint32_t* a = &fGenID;
         const uint32_t* b = &other.fGenID;
         for (int i = 0; i < 7; ++i) {
             if (a[i] < b[i]) {
                 return true;
             }
             if (a[i] > b[i]) {
@@ skipping 708 matching lines @@
     return SkScaledImageCache::GetBytesUsed();
 }
 
 size_t SkGraphics::GetImageCacheByteLimit() {
     return SkScaledImageCache::GetByteLimit();
 }
 
 size_t SkGraphics::SetImageCacheByteLimit(size_t newLimit) {
     return SkScaledImageCache::SetByteLimit(newLimit);
 }