skia: Added chrome implementation of SkDiscardableMemory.

skia/ext/SkDiscardableMemory_chrome.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "SkDiscardableMemory_chrome.h"
+
+SkDiscardableMemoryChrome::SkDiscardableMemoryChrome()
+    : discardable_(new base::DiscardableMemory()) {
+}
+
+SkDiscardableMemoryChrome::~SkDiscardableMemoryChrome() {
+}
+
+bool SkDiscardableMemoryChrome::lock() {
+  base::LockDiscardableMemoryStatus status = discardable_->Lock();
+  switch (status) {
+    case base::DISCARDABLE_MEMORY_SUCCESS:
+      return true;
+    case base::DISCARDABLE_MEMORY_PURGED:
+      discardable_->Unlock();
+      return false;
+    default:
+      discardable_.reset();
+      return false;
+  }
+}
+
+void* SkDiscardableMemoryChrome::data() {
+  return discardable_->Memory();
+}
+
+void SkDiscardableMemoryChrome::unlock() {
+  discardable_->Unlock();
+}
+
+bool SkDiscardableMemoryChrome::InitializeAndLock(size_t bytes) {
+  return discardable_->InitializeAndLock(bytes);
+}
+
+SkDiscardableMemory* SkDiscardableMemory::Create(size_t bytes) {
+  if (!base::DiscardableMemory::Supported()) {
+    return NULL;
+  }
+  scoped_ptr<SkDiscardableMemoryChrome> discardable(
+      new SkDiscardableMemoryChrome());
+  if (discardable->InitializeAndLock(bytes))
+    return discardable.release();
+  return NULL;
+}