Some usability ideas around SkTHash.

src/gpu/gl/GrGLCaps.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 GrGLCaps_DEFINED
 #define GrGLCaps_DEFINED
@@ skipping 385 matching lines @@
     struct ReadPixelsSupportedFormat {
         GrGLenum fFormat;
         GrGLenum fType;
         GrGLenum fFboFormat;
 
         bool operator==(const ReadPixelsSupportedFormat& rhs) const {
             return fFormat    == rhs.fFormat
                 && fType      == rhs.fType
                 && fFboFormat == rhs.fFboFormat;
         }
-        static uint32_t Hash(const ReadPixelsSupportedFormat& r) {
-            return SkChecksum::Murmur3(reinterpret_cast<const uint32_t*>(&r), sizeof(r));
-        }
     };
-
-    mutable SkTHashMap<ReadPixelsSupportedFormat, bool, ReadPixelsSupportedFormat::Hash>
-        fReadPixelsSupportedCache;
+    mutable SkTHashMap<ReadPixelsSupportedFormat, bool> fReadPixelsSupportedCache;
 
     typedef GrDrawTargetCaps INHERITED;
 };
 
 #endif