Re-land: base: Introduce an explicit call for reducing emulated discardable memory usage.

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 {
 
 // This is admittedly pretty magical.
 const size_t kEmulatedMemoryLimit = 512 * 1024 * 1024;
 const size_t kEmulatedSoftMemoryLimit = 32 * 1024 * 1024;
-const size_t kEmulatedBytesToKeepUnderModeratePressure = 4 * 1024 * 1024;
 const size_t kEmulatedHardMemoryLimitExpirationTimeMs = 1000;
 
 struct SharedState {
   SharedState()
       : manager(kEmulatedMemoryLimit,
                 kEmulatedSoftMemoryLimit,
-                kEmulatedBytesToKeepUnderModeratePressure,
                 TimeDelta::FromMilliseconds(
                     kEmulatedHardMemoryLimitExpirationTimeMs)) {}
 
   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_shared_state.Pointer()->manager.Register(this, bytes);
 }
 
 DiscardableMemoryEmulated::~DiscardableMemoryEmulated() {
   if (is_locked_)
     Unlock();
   g_shared_state.Pointer()->manager.Unregister(this);
 }
 
 // static
-void DiscardableMemoryEmulated::RegisterMemoryPressureListeners() {
-  g_shared_state.Pointer()->manager.RegisterMemoryPressureListener();
-}
-
-// static
-void DiscardableMemoryEmulated::UnregisterMemoryPressureListeners() {
-  g_shared_state.Pointer()->manager.UnregisterMemoryPressureListener();
-}
-
-// static
 bool DiscardableMemoryEmulated::ReduceMemoryUsage() {
   return g_shared_state.Pointer()->manager.ReduceMemoryUsage();
 }
 
 // static
+void DiscardableMemoryEmulated::ReduceMemoryUsageUntilWithinLimit(
+    size_t bytes) {
+  g_shared_state.Pointer()->manager.ReduceMemoryUsageUntilWithinLimit(bytes);
+}
+
+// static
 void DiscardableMemoryEmulated::PurgeForTesting() {
   g_shared_state.Pointer()->manager.PurgeAll();
 }
 
 bool DiscardableMemoryEmulated::Initialize() {
   return Lock() != DISCARDABLE_MEMORY_LOCK_STATUS_FAILED;
 }
 
 DiscardableMemoryLockStatus DiscardableMemoryEmulated::Lock() {
   DCHECK(!is_locked_);
@@ skipping 26 matching lines @@
   memory_.reset(new uint8[bytes_]);
   return false;
 }
 
 void DiscardableMemoryEmulated::Purge() {
   memory_.reset();
 }
 
 }  // namespace internal
 }  // namespace base