base: Use DiscardableMemoryManager on MacOSX.

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_emulated.h"
 
 #include "base/lazy_instance.h"
 #include "base/memory/discardable_memory_manager.h"
 
 namespace base {
 namespace {
 
-base::LazyInstance<internal::DiscardableMemoryManager>::Leaky g_manager =
-    LAZY_INSTANCE_INITIALIZER;
+// This is admittedly pretty magical. It's approximately enough memory for four
+// 2560x1600 images.
+const size_t kEmulatedMemoryLimit = 64 * 1024 * 1024;
+const size_t kEmulatedBytesToKeepUnderModeratePressure =
+    kEmulatedMemoryLimit / 4;
+
+struct SharedState {
+  SharedState()
+      : manager(kEmulatedMemoryLimit,
+                kEmulatedBytesToKeepUnderModeratePressure) {}
+
+  internal::DiscardableMemoryManager manager;
+};
+LazyInstance<SharedState>::Leaky g_shared_state = LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
 namespace internal {
 
 DiscardableMemoryEmulated::DiscardableMemoryEmulated(size_t bytes)
     : bytes_(bytes),
       is_locked_(false) {
-  g_manager.Pointer()->Register(this, bytes);
+  g_shared_state.Pointer()->manager.Register(this, bytes);
 }
 
 DiscardableMemoryEmulated::~DiscardableMemoryEmulated() {
   if (is_locked_)
     Unlock();
-  g_manager.Pointer()->Unregister(this);
+  g_shared_state.Pointer()->manager.Unregister(this);
 }
 
 // static
 void DiscardableMemoryEmulated::RegisterMemoryPressureListeners() {
-  g_manager.Pointer()->RegisterMemoryPressureListener();
+  g_shared_state.Pointer()->manager.RegisterMemoryPressureListener();
 }
 
 // static
 void DiscardableMemoryEmulated::UnregisterMemoryPressureListeners() {
-  g_manager.Pointer()->UnregisterMemoryPressureListener();
+  g_shared_state.Pointer()->manager.UnregisterMemoryPressureListener();
 }
 
 // static
 void DiscardableMemoryEmulated::PurgeForTesting() {
-  g_manager.Pointer()->PurgeAll();
+  g_shared_state.Pointer()->manager.PurgeAll();
 }
 
 bool DiscardableMemoryEmulated::Initialize() {
   return Lock() == DISCARDABLE_MEMORY_LOCK_STATUS_PURGED;
 }
 
 DiscardableMemoryLockStatus DiscardableMemoryEmulated::Lock() {
   DCHECK(!is_locked_);
 
   bool purged = false;
-  if (!g_manager.Pointer()->AcquireLock(this, &purged))
+  if (!g_shared_state.Pointer()->manager.AcquireLock(this, &purged))
     return DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 
   is_locked_ = true;
   return purged ? DISCARDABLE_MEMORY_LOCK_STATUS_PURGED
                 : DISCARDABLE_MEMORY_LOCK_STATUS_SUCCESS;
 }
 
 void DiscardableMemoryEmulated::Unlock() {
   DCHECK(is_locked_);
-  g_manager.Pointer()->ReleaseLock(this);
+  g_shared_state.Pointer()->manager.ReleaseLock(this);
   is_locked_ = false;
 }
 
 void* DiscardableMemoryEmulated::Memory() const {
   DCHECK(is_locked_);
   DCHECK(memory_);
   return memory_.get();
 }
 
 bool DiscardableMemoryEmulated::AllocateAndAcquireLock() {
   if (memory_)
     return true;
 
   memory_.reset(new uint8[bytes_]);
   return false;
 }
 
 void DiscardableMemoryEmulated::Purge() {
   memory_.reset();
 }
 
 }  // namespace internal
 }  // namespace base