Add request cache to SkFontHost_fontconfig.

src/core/SkResourceCache.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkResourceCache_DEFINED
 #define SkResourceCache_DEFINED
 
@@ skipping 11 matching lines @@
  *  Multiple caches can be instantiated, but each instance is not implicitly
  *  thread-safe, so if a given instance is to be shared across threads, the
  *  caller must manage the access itself (e.g. via a mutex).
  *
  *  As a convenience, a global instance is also defined, which can be safely
  *  access across threads via the static methods (e.g. FindAndLock, etc.).
  */
 class SkResourceCache {
 public:
     struct Key {
-        // Call this to access your private contents. Must not use the address after calling init()
-        void* writableContents() { return this + 1; }
+        /** Key subclasses must call this after their own fields and data are initialized.
+         *  All fields and data must be tightly packed.
+         *  @param nameSpace must be unique per Key subclass.
+         *  @param sharedID == 0 means ignore this field, does not support group purging.
+         *  @param dataSize is size of fields and data of the subclass, must be a multiple of 4.
+         */
+        void init(void* nameSpace, uint64_t sharedID, size_t dataSize);
 
-        // must call this after your private data has been written.
-        // nameSpace must be unique per Key subclass.
-        // sharedID == 0 means ignore this field : does not support group purging.
-        // length must be a multiple of 4
-        void init(void* nameSpace, uint64_t sharedID, size_t length);
+        /** Returns the size of this key. */
+        size_t size() const {
+            return fCount32 << 2;
+        }
 
         void* getNamespace() const { return fNamespace; }
         uint64_t getSharedID() const { return ((uint64_t)fSharedID_hi << 32) | fSharedID_lo; }
 
         // This is only valid after having called init().
         uint32_t hash() const { return fHash; }
 
         bool operator==(const Key& other) const {
             const uint32_t* a = this->as32();
             const uint32_t* b = other.as32();
@@ skipping 227 matching lines @@
 
     void init();    // called by constructors
 
 #ifdef SK_DEBUG
     void validate() const;
 #else
     void validate() const {}
 #endif
 };
 #endif