Re-land: base: Enable browser-wide discardable memory on Linux, CrOS and Windows.

base/memory/discardable_memory_mac.cc

 // Copyright (c) 2013 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 "base/memory/discardable_memory.h"
 
 #include "base/logging.h"
 #include "base/memory/discardable_memory_emulated.h"
 #include "base/memory/discardable_memory_mach.h"
 #include "base/memory/discardable_memory_manager.h"
@@ skipping 10 matching lines @@
 // static
 bool DiscardableMemory::ReduceMemoryUsage() {
   return internal::DiscardableMemoryEmulated::ReduceMemoryUsage();
 }
 
 // static
 void DiscardableMemory::GetSupportedTypes(
     std::vector<DiscardableMemoryType>* types) {
   const DiscardableMemoryType supported_types[] = {
     DISCARDABLE_MEMORY_TYPE_MACH,
-    DISCARDABLE_MEMORY_TYPE_EMULATED,
-    DISCARDABLE_MEMORY_TYPE_SHMEM
+    DISCARDABLE_MEMORY_TYPE_SHMEM,
+    DISCARDABLE_MEMORY_TYPE_EMULATED
   };
   types->assign(supported_types, supported_types + arraysize(supported_types));
 }
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemoryWithType(
     DiscardableMemoryType type, size_t size) {
   switch (type) {
     case DISCARDABLE_MEMORY_TYPE_MACH: {
       scoped_ptr<internal::DiscardableMemoryMach> memory(
@@ skipping 30 matching lines @@
 }
 
 // static
 void DiscardableMemory::PurgeForTesting() {
   internal::DiscardableMemoryMach::PurgeForTesting();
   internal::DiscardableMemoryEmulated::PurgeForTesting();
   internal::DiscardableMemoryShmem::PurgeForTesting();
 }
 
 }  // namespace base