Add discardable memory emulation for non-android/mac platforms

base/memory/discardable_memory_android.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 <sys/mman.h>
 #include <unistd.h>
 
 #include "base/basictypes.h"
@@ skipping 117 matching lines @@
   const int fd_;
   void* const memory_;
   const size_t size_;
 
   DISALLOW_COPY_AND_ASSIGN(DiscardableMemoryAndroid);
 };
 
 }  // namespace
 
 // static
-bool DiscardableMemory::Supported() {
+bool DiscardableMemory::SupportedNatively() {
   return true;
 }
 
 // static
 scoped_ptr<DiscardableMemory> DiscardableMemory::CreateLockedMemory(
     size_t size) {
   // Pinning & unpinning works with page granularity therefore align the size
   // upfront.
   const size_t kPageSize = 4096;
   const size_t mask = ~(kPageSize - 1);
@@ skipping 10 matching lines @@
 bool DiscardableMemory::PurgeForTestingSupported() {
   return false;
 }
 
 // static
 void DiscardableMemory::PurgeForTesting() {
   NOTIMPLEMENTED();
 }
 
 }  // namespace base