Apply artificial memory pressure when backgrounded.

content/renderer/render_process_visibility_manager.h

Index: content/renderer/render_process_visibility_manager.h
diff --git a/content/renderer/render_process_visibility_manager.h b/content/renderer/render_process_visibility_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..7cd9581b1d139d4401ea90d073da36e5652c7bbd
--- /dev/null
+++ b/content/renderer/render_process_visibility_manager.h
@@ -0,0 +1,32 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[Avi (use Gerrit), 2013/06/20 20:34:27]

New files don't get "(c)", use current year.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_RENDERER_RENDER_PROCESS_VISIBILITY_MANAGER_H_
+#define CONTENT_RENDERER_RENDER_PROCESS_VISIBILITY_MANAGER_H_
+
+#include "base/memory/singleton.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class CONTENT_EXPORT RenderProcessVisibilityManager {
+ public:
+  static RenderProcessVisibilityManager* GetInstance();
+
+  void WidgetVisibilityChanged(bool visible);
+
+ private:
+  friend struct DefaultSingletonTraits<RenderProcessVisibilityManager>;
+
+  RenderProcessVisibilityManager();
+  ~RenderProcessVisibilityManager();
+
+  int num_visible_render_widgets_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderProcessVisibilityManager);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_RENDER_PROCESS_VISIBILITY_MANAGER_H_