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

components/rappor/content/common/rappor_messages.h

Index: components/rappor/content/common/rappor_messages.h
diff --git a/components/rappor/content/common/rappor_messages.h b/components/rappor/content/common/rappor_messages.h
new file mode 100644
index 0000000000000000000000000000000000000000..79b5e03938ae7422ddc58a6738bb3c090643c1db
--- /dev/null
+++ b/components/rappor/content/common/rappor_messages.h
@@ -0,0 +1,20 @@
+// Copyright (c) 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// IPC messages for RAPPOR.
+// Multiply-included message file, hence no include guard.
+
+#include "content/common/content_export.h"
+#include "ipc/ipc_message_macros.h"
+
+#undef IPC_MESSAGE_EXPORT
+#define IPC_MESSAGE_EXPORT CONTENT_EXPORT
+#define IPC_MESSAGE_START RapporMsgStart
+
+// Messages sent from the renderer to the browser.
+
+// Record a sample string to RAPPOR.
+IPC_MESSAGE_CONTROL2(RapporHostMsg_RecordSample,
+                     std::string /* metric */,
+                     std::string /* sample */)