Add an IPC method for Blink to call RapporService::RecordSample()

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index db273e76bb705e9b5bc7a19613c43f60713cef19..f43d99c491ae4f1fe212b259fb43af39eab2f83c 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -1498,6 +1498,11 @@ IPC_MESSAGE_ROUTED3(ViewHostMsg_UnregisterProtocolHandler,
 IPC_MESSAGE_CONTROL1(ViewHostMsg_UserMetricsRecordAction,
                      std::string /* action */)
 
+// Send back a string to be recorded by UserMetrics.
+IPC_MESSAGE_CONTROL2(ViewHostMsg_UserMetricsRecordRappor,
+                     std::string /* metric */,
+                     std::string /* sample */)
+
 // Notifies the browser that the page was or was not saved as MHTML.
 IPC_MESSAGE_CONTROL2(ViewHostMsg_SavedPageAsMHTML,
                      int /* job_id */,