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

content/renderer/render_thread_impl.cc

 // Copyright (c) 2012 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 "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
 
 #include "base/allocator/allocator_extension.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/discardable_memory.h"
+#include "base/memory/discardable_memory_emulated.h"
 #include "base/memory/shared_memory.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/stats_table.h"
 #include "base/path_service.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_local.h"
@@ skipping 499 matching lines @@
                   supported_types.end(),
                   requested_type) != supported_types.end()) {
       type = requested_type;
     } else {
       LOG(ERROR) << "Requested discardable memory type is not supported.";
     }
   }
 
   base::DiscardableMemory::SetPreferredType(type);
 
-  // Allow discardable memory implementations to register memory pressure
-  // listeners.
-  base::DiscardableMemory::RegisterMemoryPressureListeners();
-
   // AllocateGpuMemoryBuffer must be used exclusively on one thread but
   // it doesn't have to be the same thread RenderThreadImpl is created on.
   allocate_gpu_memory_buffer_thread_checker_.DetachFromThread();
 
   if (command_line.HasSwitch(switches::kNumRasterThreads)) {
     int num_raster_threads;
     std::string string_value =
         command_line.GetSwitchValueASCII(switches::kNumRasterThreads);
     if (base::StringToInt(string_value, &num_raster_threads) &&
         num_raster_threads >= kMinRasterThreads &&
@@ skipping 1051 matching lines @@
 
 void RenderThreadImpl::WidgetDestroyed() {
   widget_count_--;
 }
 
 void RenderThreadImpl::WidgetHidden() {
   DCHECK_LT(hidden_widget_count_, widget_count_);
   hidden_widget_count_++;
 
   if (widget_count_ && hidden_widget_count_ == widget_count_) {
+    // We emulate a "moderate memory pressure" event for emulated discardable
+    // memory to make sure that background tabs don't use too much memory.
+    base::DiscardableMemoryEmulated::
+        ReduceMemoryUsageUntilWithinModeratePressureLimit();
+
     if (GetContentClient()->renderer()->RunIdleHandlerWhenWidgetsHidden())
       ScheduleIdleHandler(kInitialIdleHandlerDelayMs);
   }
 }
 
 void RenderThreadImpl::WidgetRestored() {
   DCHECK_GT(hidden_widget_count_, 0);
   hidden_widget_count_--;
 
   if (!GetContentClient()->renderer()->RunIdleHandlerWhenWidgetsHidden()) {
     return;
   }
 
   ScheduleIdleHandler(kLongIdleHandlerDelayMs);
 }
 
 }  // namespace content