memory coordinator: Purge memory under memory pressure

chrome/browser/memory/chrome_memory_coordinator_delegate.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 CHROME_BROWSER_MEMORY_CHROME_MEMORY_COORDINATOR_DELEGATE_H_
 #define CHROME_BROWSER_MEMORY_CHROME_MEMORY_COORDINATOR_DELEGATE_H_
 
 #include "base/memory/weak_ptr.h"
 #include "content/public/browser/memory_coordinator_delegate.h"
 
 namespace memory {
 
 // A MemoryCoordinatorDelegate which uses TabManager internally.
 class ChromeMemoryCoordinatorDelegate
     : public content::MemoryCoordinatorDelegate {
  public:
   static std::unique_ptr<content::MemoryCoordinatorDelegate> Create();
 
   ~ChromeMemoryCoordinatorDelegate() override;
 
   // MemoryCoordinatorDelegate implementation.
   bool CanSuspendBackgroundedRenderer(int render_process_id) override;
-  void DiscardTab() override;
+  bool DiscardTab() override;
 
  private:
   ChromeMemoryCoordinatorDelegate();
 
   DISALLOW_COPY_AND_ASSIGN(ChromeMemoryCoordinatorDelegate);
 };
 
 }  // namespace memory
 
 #endif  // CHROME_BROWSER_MEMORY_CHROME_MEMORY_COORDINATOR_DELEGATE_H_