[Not for review] Discardable memory emulation

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 0f86870fba07207c47a15003c8884158e750c6e3..4b1958bc76eff54b8890a6698f8a2ebe9f7b25a7 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -14,6 +14,7 @@
 #include "base/debug/trace_event.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/memory/discardable_memory.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/stats_table.h"
@@ -68,7 +69,9 @@
 #include "content/renderer/memory_benchmarking_extension.h"
 #include "content/renderer/p2p/socket_dispatcher.h"
 #include "content/renderer/plugin_channel_host.h"
+#include "content/renderer/render_process_discardable_memory_provider.h"
 #include "content/renderer/render_process_impl.h"
+#include "content/renderer/render_process_visibility_manager.h"
 #include "content/renderer/render_view_impl.h"
 #include "content/renderer/renderer_webkitplatformsupport_impl.h"
 #include "content/renderer/skia_benchmarking_extension.h"
@@ -400,6 +403,13 @@ void RenderThreadImpl::Init() {
     RegisterExtension(MemoryBenchmarkingExtension::Get());
 #endif  // USE_TCMALLOC
 
+  if (!base::DiscardableMemoryProvider::GetInstance()) {

[Avi (use Gerrit), 2013/06/07 14:46:53]

DISCARDABLE_MEMORY_SUPPORTED_NATIVELY?

But only if we want to say in the .h that iff
DISCARDABLE_MEMORY_SUPPORTED_NATIVELY then GetInstance is guaranteed to succeed.
Which might not be true if we decide to have a Win8 impl.

+    discardable_provider_.reset(new RenderProcessDiscardableMemoryProvider);
+    RenderProcessVisibilityManager::GetInstance()->AddObserver(
+        discardable_provider_.get());
+    base::DiscardableMemoryProvider::SetInstance(discardable_provider_.get());
+  }
+
   if (command_line.HasSwitch(switches::kEnableSkiaBenchmarking)) {
     LOG(WARNING) << "Enabling unsafe Skia benchmarking extension.";
     RegisterExtension(SkiaBenchmarkingExtension::Get());
@@ -418,6 +428,8 @@ void RenderThreadImpl::Init() {
 }
 
 RenderThreadImpl::~RenderThreadImpl() {
+  if (discardable_provider_)
+    base::DiscardableMemoryProvider::SetInstance(NULL);
 }
 
 void RenderThreadImpl::Shutdown() {
@@ -617,6 +629,12 @@ void RenderThreadImpl::WidgetHidden() {
   DCHECK(hidden_widget_count_ < widget_count_);
   hidden_widget_count_++;
 
+  if (discardable_provider_) {
+    RenderProcessVisibilityManager* manager =
+        RenderProcessVisibilityManager::GetInstance();
+    manager->WidgetVisibilityChanged(false);
+  }
+
   if (!GetContentClient()->renderer()->RunIdleHandlerWhenWidgetsHidden()) {
     return;
   }
@@ -628,6 +646,13 @@ void RenderThreadImpl::WidgetHidden() {
 void RenderThreadImpl::WidgetRestored() {
   DCHECK_GT(hidden_widget_count_, 0);
   hidden_widget_count_--;
+
+  if (discardable_provider_) {
+    RenderProcessVisibilityManager* manager =
+        RenderProcessVisibilityManager::GetInstance();
+    manager->WidgetVisibilityChanged(true);
+  }
+
   if (!GetContentClient()->renderer()->RunIdleHandlerWhenWidgetsHidden()) {
     return;
   }