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

base/memory/discardable_memory_manager.cc

 // Copyright 2014 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_manager.h"
 
 #include "base/bind.h"
 #include "base/containers/hash_tables.h"
 #include "base/containers/mru_cache.h"
 #include "base/debug/crash_logging.h"
@@ skipping 17 matching lines @@
           bytes_to_keep_under_moderate_pressure),
       hard_memory_limit_expiration_time_(hard_memory_limit_expiration_time) {
   BytesAllocatedChanged(bytes_allocated_);
 }
 
 DiscardableMemoryManager::~DiscardableMemoryManager() {
   DCHECK(allocations_.empty());
   DCHECK_EQ(0u, bytes_allocated_);
 }
 
-void DiscardableMemoryManager::RegisterMemoryPressureListener() {
-  AutoLock lock(lock_);
-  DCHECK(base::MessageLoop::current());
-  DCHECK(!memory_pressure_listener_);
-  memory_pressure_listener_.reset(new MemoryPressureListener(base::Bind(
-      &DiscardableMemoryManager::OnMemoryPressure, Unretained(this))));
-}
-
-void DiscardableMemoryManager::UnregisterMemoryPressureListener() {
-  AutoLock lock(lock_);
-  DCHECK(memory_pressure_listener_);
-  memory_pressure_listener_.reset();
-}
-
 void DiscardableMemoryManager::SetMemoryLimit(size_t bytes) {
   AutoLock lock(lock_);
   memory_limit_ = bytes;
   PurgeIfNotUsedSinceTimestampUntilUsageIsWithinLimitWithLockAcquired(
       Now(), memory_limit_);
 }
 
 void DiscardableMemoryManager::SetSoftMemoryLimit(size_t bytes) {
   AutoLock lock(lock_);
   soft_memory_limit_ = bytes;
 }
 
 void DiscardableMemoryManager::SetBytesToKeepUnderModeratePressure(
     size_t bytes) {
   AutoLock lock(lock_);
   bytes_to_keep_under_moderate_pressure_ = bytes;
 }
 
 void DiscardableMemoryManager::SetHardMemoryLimitExpirationTime(
     TimeDelta hard_memory_limit_expiration_time) {
   AutoLock lock(lock_);
   hard_memory_limit_expiration_time_ = hard_memory_limit_expiration_time;
 }
 
 bool DiscardableMemoryManager::ReduceMemoryUsage() {
   return PurgeIfNotUsedSinceHardLimitCutoffUntilWithinSoftMemoryLimit();
 }
 
+void
+DiscardableMemoryManager::ReduceMemoryUsageUntilWithinModeratePressureLimit() {
+  PurgeUntilWithinBytesToKeepUnderModeratePressure();
+}
+
 void DiscardableMemoryManager::Register(Allocation* allocation, size_t bytes) {
   AutoLock lock(lock_);
-  // A registered memory listener is currently required. This DCHECK can be
-  // moved or removed if we decide that it's useful to relax this condition.
-  // TODO(reveman): Enable this DCHECK when skia and blink are able to
-  // register memory pressure listeners. crbug.com/333907
-  // DCHECK(memory_pressure_listener_);
   DCHECK(allocations_.Peek(allocation) == allocations_.end());
   allocations_.Put(allocation, AllocationInfo(bytes));
 }
 
 void DiscardableMemoryManager::Unregister(Allocation* allocation) {
   AutoLock lock(lock_);
   AllocationMap::iterator it = allocations_.Peek(allocation);
   DCHECK(it != allocations_.end());
   const AllocationInfo& info = it->second;
 
@@ skipping 78 matching lines @@
   AutoLock lock(lock_);
   AllocationMap::const_iterator it = allocations_.Peek(allocation);
   return it != allocations_.end() && it->second.purgable;
 }
 
 size_t DiscardableMemoryManager::GetBytesAllocatedForTest() const {
   AutoLock lock(lock_);
   return bytes_allocated_;
 }
 
-void DiscardableMemoryManager::OnMemoryPressure(
-    MemoryPressureListener::MemoryPressureLevel pressure_level) {
-  switch (pressure_level) {
-    case MemoryPressureListener::MEMORY_PRESSURE_MODERATE:
-      PurgeUntilWithinBytesToKeepUnderModeratePressure();
-      return;
-    case MemoryPressureListener::MEMORY_PRESSURE_CRITICAL:
-      PurgeAll();
-      return;
-  }
-
-  NOTREACHED();
-}
-
 void
 DiscardableMemoryManager::PurgeUntilWithinBytesToKeepUnderModeratePressure() {
   AutoLock lock(lock_);
 
   PurgeIfNotUsedSinceTimestampUntilUsageIsWithinLimitWithLockAcquired(
       Now(), bytes_to_keep_under_moderate_pressure_);
 }
 
 bool DiscardableMemoryManager::
     PurgeIfNotUsedSinceHardLimitCutoffUntilWithinSoftMemoryLimit() {
@@ skipping 45 matching lines @@
   base::debug::SetCrashKeyValue(kDiscardableMemoryUsageKey,
                                 Uint64ToString(new_bytes_allocated));
 }
 
 TimeTicks DiscardableMemoryManager::Now() const {
   return TimeTicks::Now();
 }
 
 }  // namespace internal
 }  // namespace base