Add discardable memory emulation for non-android/mac platforms

skia/ext/SkDiscardableMemory_chrome.cc

 // Copyright 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 "SkDiscardableMemory_chrome.h"
 
 SkDiscardableMemoryChrome::~SkDiscardableMemoryChrome() {}
 
 bool SkDiscardableMemoryChrome::lock() {
   const base::LockDiscardableMemoryStatus status = discardable_->Lock();
@@ skipping 16 matching lines @@
 void SkDiscardableMemoryChrome::unlock() {
   discardable_->Unlock();
 }
 
 SkDiscardableMemoryChrome::SkDiscardableMemoryChrome(
     scoped_ptr<base::DiscardableMemory> memory)
     : discardable_(memory.Pass()) {
 }
 
 SkDiscardableMemory* SkDiscardableMemory::Create(size_t bytes) {
-  if (!base::DiscardableMemory::Supported())
-    return NULL;
   scoped_ptr<base::DiscardableMemory> discardable(
       base::DiscardableMemory::CreateLockedMemory(bytes));
   if (!discardable)
     return NULL;
   return new SkDiscardableMemoryChrome(discardable.Pass());
 }