Add discardable memory emulation for non-android/mac platforms

base/memory/discardable_memory_emulated.cc

+// Copyright 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 "base/memory/discardable_memory.h"
+
+#include "base/memory/discardable_memory_provider.h"
+
+namespace base {
+
+// static
+bool DiscardableMemory::SupportedNatively() {
+  return false;
+}
+
+DiscardableMemory::~DiscardableMemory() {
+  if (is_locked())
+    Unlock();
+  if (memory_)
+    Deallocate();
+  DiscardableMemoryProvider::GetInstance()->Unregister(this);
+}
+
+bool DiscardableMemory::InitializeAndLock(size_t size) {
+  DiscardableMemoryProvider::GetInstance()->Register(this);
+  size_ = size;
+  return Lock() == DISCARDABLE_MEMORY_PURGED;
+}
+
+LockDiscardableMemoryStatus DiscardableMemory::Lock() {
+  DCHECK(!is_locked_);
+
+  // This can fail if we have not been registered. That is, it's an error to
+  // |Lock| before calling |InitializeAndLock|.
+  if (!DiscardableMemoryProvider::GetInstance()->DidAccess(this))
+    return DISCARDABLE_MEMORY_FAILED;
+
+  is_locked_ = true;
+  if (memory_)
+    return DISCARDABLE_MEMORY_SUCCESS;
+
+  if (Allocate())
+    return DISCARDABLE_MEMORY_PURGED;
+
+  is_locked_ = false;
+  return DISCARDABLE_MEMORY_FAILED;
+}
+
+void DiscardableMemory::Unlock() {
+  DCHECK(is_locked_);
+  DiscardableMemoryProvider::GetInstance()->DidAccess(this);
+  is_locked_ = false;
+}
+
+bool DiscardableMemory::Allocate() {
+  DCHECK(!memory_);
+  DiscardableMemoryProvider* provider =
+      DiscardableMemoryProvider::GetInstance();
+
+  if (size_ == 0)
+    return false;
+
+  size_t limit = provider->discardable_memory_limit();
+  if (limit > 0 && size_ > limit)
+    return false;
+
+  memory_ = malloc(size_);
+  if (memory_)
+    provider->DidAllocate(size_);
+
+  return memory_;
+}
+
+void DiscardableMemory::Deallocate() {
+  DCHECK(memory_);
+  free(memory_);
+  memory_ = NULL;
+  DiscardableMemoryProvider::GetInstance()->DidDeallocate(size_);
+}
+
+// static
+bool DiscardableMemory::PurgeForTestingSupported() {
+  return true;
+}
+
+// static
+void DiscardableMemory::PurgeForTesting() {
+  DiscardableMemoryProvider::GetInstance()->PurgeAll();
+}
+
+}  // namespace base