memory_coordinator: Discard tabs under critical memory condition

chrome/browser/memory/tab_manager.cc

 // Copyright (c) 2012 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/tab_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 332 matching lines @@
       return false;
   }
 
   // Do not discard a tab that was explicitly disallowed to.
   if (!IsTabAutoDiscardable(web_contents))
     return false;
 
   return true;
 }
 
-void TabManager::DiscardTab() {
+bool TabManager::DiscardTab() {
 #if defined(OS_CHROMEOS)
   // Call Chrome OS specific low memory handling process.
   if (base::FeatureList::IsEnabled(features::kArcMemoryManagement)) {
     delegate_->LowMemoryKill(GetUnsortedTabStats());
-    return;
+    return false;
   }
 #endif
-  DiscardTabImpl();
+  return DiscardTabImpl() != nullptr;
 }
 
 WebContents* TabManager::DiscardTabById(int64_t target_web_contents_id) {
   TabStripModel* model;
   int index = FindTabStripModelById(target_web_contents_id, &model);
 
   if (index == -1)
     return nullptr;
 
   VLOG(1) << "Discarding tab " << index << " id " << target_web_contents_id;
@@ skipping 659 matching lines @@
   // platform.
   std::string allow_multiple_discards = variations::GetVariationParamValue(
       features::kAutomaticTabDiscarding.name, "AllowMultipleDiscards");
   return (allow_multiple_discards != "true");
 #else
   return false;
 #endif
 }
 
 }  // namespace memory