Revert "Revert 3 mac autofill CLs."

components/autofill/content/renderer/autofill_agent.cc

Index: components/autofill/content/renderer/autofill_agent.cc
diff --git a/components/autofill/content/renderer/autofill_agent.cc b/components/autofill/content/renderer/autofill_agent.cc
index 6d48fb5cbe547227cf97b8985e063497ca880eb6..525bc3fe967181cec42c7503857d3a924417c4b9 100644
--- a/components/autofill/content/renderer/autofill_agent.cc
+++ b/components/autofill/content/renderer/autofill_agent.cc
@@ -150,6 +150,7 @@ AutofillAgent::~AutofillAgent() {}
 bool AutofillAgent::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(AutofillAgent, message)
+    IPC_MESSAGE_HANDLER(AutofillMsg_Ping, OnPing)
     IPC_MESSAGE_HANDLER(AutofillMsg_FillForm, OnFillForm)
     IPC_MESSAGE_HANDLER(AutofillMsg_PreviewForm, OnPreviewForm)
     IPC_MESSAGE_HANDLER(AutofillMsg_FieldTypePredictionsAvailable,
@@ -455,6 +456,10 @@ void AutofillAgent::OnFillForm(int query_id, const FormData& form) {
                                                    base::TimeTicks::Now()));
 }
 
+void AutofillAgent::OnPing() {
+  Send(new AutofillHostMsg_PingAck(routing_id()));
+}
+
 void AutofillAgent::OnPreviewForm(int query_id, const FormData& form) {
   if (!render_view()->GetWebView() || query_id != autofill_query_id_)
     return;