Use SharedPersistentMemoryAllocator to share field trial state

content/public/browser/browser_child_process_host.h

Index: content/public/browser/browser_child_process_host.h
diff --git a/content/public/browser/browser_child_process_host.h b/content/public/browser/browser_child_process_host.h
index 67c55acf63430fdee58a4467134b38544d003424..d494be5be9b14b891bcbe62dade14dcb2909d216 100644
--- a/content/public/browser/browser_child_process_host.h
+++ b/content/public/browser/browser_child_process_host.h
@@ -63,12 +63,9 @@ class CONTENT_EXPORT BrowserChildProcessHost : public IPC::Sender {
   ~BrowserChildProcessHost() override {}
 
   // Derived classes call this to launch the child process asynchronously.
-  // Takes ownership of |cmd_line| and |delegate|. Takes in |field_trial_state|
-  // to explicitly pass its handle to be inherited on Windows to the child
-  // process via the command line.
+  // Takes ownership of |cmd_line| and |delegate|.
   virtual void Launch(SandboxedProcessLauncherDelegate* delegate,
                       base::CommandLine* cmd_line,
-                      const base::SharedMemory* field_trial_state,
                       bool terminate_on_shutdown) = 0;
 
   virtual const ChildProcessData& GetData() const = 0;