Use SharedPersistentMemoryAllocator to share field trial state

content/browser/renderer_host/render_process_host_impl.h

 // 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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 540 matching lines @@
   // for UMA.
   size_t max_worker_count_;
 
   // Context shared for each mojom::PermissionService instance created for this
   // RPH.
   std::unique_ptr<PermissionServiceContext> permission_service_context_;
 
   // The memory allocator, if any, in which the renderer will write its metrics.
   std::unique_ptr<base::SharedPersistentMemoryAllocator> metrics_allocator_;
 
-  // Anonymous shared memory segment to share with subprocess containing list of
-  // field trials (represented as a string).
-  // TODO(crbug.com/653874): Eventually remove this and use single shared memory
-  // object across processes.
-  std::unique_ptr<base::SharedMemory> field_trial_state_;
-
   bool channel_connected_;
   bool sent_render_process_ready_;
 
 #if defined(OS_ANDROID)
   // UI thread is the source of sync IPCs and all shutdown signals.
   // Therefore a proper shutdown event to unblock the UI thread is not
   // possible without massive refactoring shutdown code.
   // Luckily Android never performs a clean shutdown. So explicitly
   // ignore this problem.
   base::WaitableEvent never_signaled_;
 #endif
 
   scoped_refptr<ResourceMessageFilter> resource_message_filter_;
 
   mojom::RouteProviderAssociatedPtr remote_route_provider_;
 
   // A WeakPtrFactory which is reset every time Cleanup() runs. Used to vend
   // WeakPtrs which are invalidated any time the RPHI is recycled.
   std::unique_ptr<base::WeakPtrFactory<RenderProcessHostImpl>>
       instance_weak_factory_;
 
   base::WeakPtrFactory<RenderProcessHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_