Revert "Revert 3 mac autofill CLs."

components/autofill/content/common/autofill_messages.h

Index: components/autofill/content/common/autofill_messages.h
diff --git a/components/autofill/content/common/autofill_messages.h b/components/autofill/content/common/autofill_messages.h
index cb9fc6a1252f615b3c57377c77dbfdbc73807f28..f9a99fe670dea7fccaf93328f7517227906990e1 100644
--- a/components/autofill/content/common/autofill_messages.h
+++ b/components/autofill/content/common/autofill_messages.h
@@ -94,6 +94,11 @@ IPC_ENUM_TRAITS_MAX_VALUE(
 
 // Autofill messages sent from the browser to the renderer.
 
+// Instructs the renderer to immediately return an IPC acknowledging the ping.
+// This is used to correctly sequence events, since IPCs are guaranteed to be
+// processed in order.
+IPC_MESSAGE_ROUTED0(AutofillMsg_Ping)
+
 // Instructs the renderer to fill the active form with the given form data.
 IPC_MESSAGE_ROUTED2(AutofillMsg_FillForm,
                     int /* query_id */,
@@ -227,6 +232,9 @@ IPC_MESSAGE_ROUTED5(AutofillHostMsg_QueryFormFieldAutofill,
 // Sent when a form is previewed with Autofill suggestions.
 IPC_MESSAGE_ROUTED0(AutofillHostMsg_DidPreviewAutofillFormData)
 
+// Sent immediately after the renderer receives a ping IPC.
+IPC_MESSAGE_ROUTED0(AutofillHostMsg_PingAck)
+
 // Sent when a form is filled with Autofill suggestions.
 IPC_MESSAGE_ROUTED1(AutofillHostMsg_DidFillAutofillFormData,
                     base::TimeTicks /* timestamp */)