memory coordinator: Purge memory under memory pressure

chrome/browser/memory/chrome_memory_coordinator_delegate.cc

 // 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.
 
 #include "chrome/browser/memory/chrome_memory_coordinator_delegate.h"
 
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/memory/tab_manager.h"
 
@@ skipping 13 matching lines @@
     int render_process_id) {
 #if defined(OS_ANDROID)
   // TODO(bashi): Implement
   return true;
 #else
   return g_browser_process->GetTabManager()->CanSuspendBackgroundedRenderer(
       render_process_id);
 #endif
 }
 
-void ChromeMemoryCoordinatorDelegate::DiscardTab() {
+bool ChromeMemoryCoordinatorDelegate::DiscardTab() {
 #if !defined(OS_ANDROID)
   if (g_browser_process->GetTabManager())
-    g_browser_process->GetTabManager()->DiscardTab();
+    return g_browser_process->GetTabManager()->DiscardTab();
 #endif
+  return false;
 }
 
 }  // namespace memory