Use SharedPersistentMemoryAllocator to share field trial state

content/browser/renderer_host/render_process_host_impl.h

Index: content/browser/renderer_host/render_process_host_impl.h
diff --git a/content/browser/renderer_host/render_process_host_impl.h b/content/browser/renderer_host/render_process_host_impl.h
index f97cd70afc3b22d9cb4f2afe1a07f375661456ca..1427945f2f24e054f865afc27170e3df9b5841d0 100644
--- a/content/browser/renderer_host/render_process_host_impl.h
+++ b/content/browser/renderer_host/render_process_host_impl.h
@@ -558,12 +558,6 @@ class CONTENT_EXPORT RenderProcessHostImpl
   // 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_;