webkit: Avoid use of discardable memory unless supported natively.

webkit/child/webkitplatformsupport_child_impl.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 "webkit/child/webkitplatformsupport_child_impl.h"
 
 #include "base/memory/discardable_memory.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "webkit/child/fling_curve_configuration.h"
 #include "webkit/child/web_discardable_memory_impl.h"
@@ skipping 75 matching lines @@
 }
 
 void WebKitPlatformSupportChildImpl::didStopWorkerRunLoop(
     const WebKit::WebWorkerRunLoop& runLoop) {
   WorkerTaskRunner* worker_task_runner = WorkerTaskRunner::Instance();
   worker_task_runner->OnWorkerRunLoopStopped(runLoop);
 }
 
 WebKit::WebDiscardableMemory*
 WebKitPlatformSupportChildImpl::allocateAndLockDiscardableMemory(size_t bytes) {
+  if (!base::DiscardableMemory::SupportedNatively())
+    return NULL;
   return WebDiscardableMemoryImpl::CreateLockedMemory(bytes).release();
 }
 
 // static
 void WebKitPlatformSupportChildImpl::DestroyCurrentThread(void* thread) {
   WebThreadImplForMessageLoop* impl =
       static_cast<WebThreadImplForMessageLoop*>(thread);
   delete impl;
 }
 
 }  // namespace webkit_glue