[NotForReview] An idea for experimenting purge & suspend

content/browser/memory/memory_coordinator.h

 // Copyright 2016 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.
 
 #ifndef CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_H_
 #define CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_H_
 
 #include "base/memory/memory_coordinator_client_registry.h"
 #include "base/memory/singleton.h"
 #include "base/process/process_handle.h"
 #include "content/common/content_export.h"
 #include "content/common/memory_coordinator.mojom.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace content {
 
 // NOTE: Memory coordinator is under development and not fully working.
 // TODO(bashi): Add more explanations when we implement memory coordinator V0.
 
 class MemoryCoordinatorHandleImpl;
 
 // MemoryCoordinator is responsible for the whole memory management accross the
 // browser and child proceeses. It dispatches memory events to its clients and
 // child processes based on its best knowledge of the memory usage.
 class CONTENT_EXPORT MemoryCoordinator {
  public:
   ~MemoryCoordinator();
 
+  // Returns true when memory coordinator is enabled.
+  static bool IsEnabled();
+
   // Singleton factory/accessor.
   static MemoryCoordinator* GetInstance();
 
   // Creates a handle to the provided child process.
   void CreateHandle(int render_process_id,
                     mojom::MemoryCoordinatorHandleRequest request);
 
   // Returns number of children. Only used for testing.
   size_t NumChildrenForTesting();
 
   // Dispatches a memory state change to the provided process. Returns true if
   // the process is tracked by this coordinator and successfully dispatches,
   // returns false otherwise.
   bool SetMemoryState(
       int render_process_id, mojom::MemoryState memory_state);
 
   // Returns the memory state of the specified render process. Returns UNKNOWN
   // if the process is not tracked by this coordinator.
   mojom::MemoryState GetMemoryState(int render_process_id) const;
 
+  // Purges and suspends a child. This is an experimental mechanism and
+  // should not be exposed as an API. Returns true when memory coordinator
+  // sends a request to purge and suspend to the child process.
+  bool PurgeAndSuspendChild(int render_process_id);
+
  protected:
   // Constructor. Protected as this is a singleton, but accessible for
   // unittests.
   MemoryCoordinator();
 
   // Adds the given ChildMemoryCoordinator as a child of this coordinator.
   void AddChildForTesting(int dummy_render_process_id,
                           mojom::ChildMemoryCoordinatorPtr child);
 
   // Callback invoked by mojo when the child connection goes down. Exposed
@@ skipping 26 matching lines @@
   // MemoryCoordinator and removed automatically when an underlying binding is
   // disconnected.
   ChildInfoMap children_;
 
   DISALLOW_COPY_AND_ASSIGN(MemoryCoordinator);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_H_