Use SharedPersistentMemoryAllocator to share field trial state

content/browser/browser_child_process_host_impl.h

Index: content/browser/browser_child_process_host_impl.h
diff --git a/content/browser/browser_child_process_host_impl.h b/content/browser/browser_child_process_host_impl.h
index 6d930635d001e0174731c8f3f47c75f2e9da0327..7852609b0068af2d5ca9678fb4e86fed5fc2c5be 100644
--- a/content/browser/browser_child_process_host_impl.h
+++ b/content/browser/browser_child_process_host_impl.h
@@ -66,14 +66,12 @@ class CONTENT_EXPORT BrowserChildProcessHostImpl
   // Copies kEnableFeatures and kDisableFeatures to the command line. Generates
   // them from the FeatureList override state, to take into account overrides
   // from FieldTrials.
-  static std::unique_ptr<base::SharedMemory> CopyFeatureAndFieldTrialFlags(
-      base::CommandLine* cmd_line);
+  static void CopyFeatureAndFieldTrialFlags(base::CommandLine* cmd_line);
 
   // BrowserChildProcessHost implementation:
   bool Send(IPC::Message* message) override;
   void Launch(SandboxedProcessLauncherDelegate* delegate,
               base::CommandLine* cmd_line,
-              const base::SharedMemory* field_trial_state,
               bool terminate_on_shutdown) override;
   const ChildProcessData& GetData() const override;
   ChildProcessHost* GetHost() const override;