Add an API for hosted apps to check their install and running states.

chrome/common/extensions/extension_messages.h

Index: chrome/common/extensions/extension_messages.h
diff --git a/chrome/common/extensions/extension_messages.h b/chrome/common/extensions/extension_messages.h
index f02a95275bb24be3ab641b70acd50cd499fe645b..03ade298d32f690bcaf3133cd4bc3661363594a4 100644
--- a/chrome/common/extensions/extension_messages.h
+++ b/chrome/common/extensions/extension_messages.h
@@ -279,6 +279,11 @@ IPC_MESSAGE_ROUTED3(ExtensionMsg_GetAppNotifyChannelResponse,
                     std::string /* error */,
                     int32 /* callback_id */)
 
+// Response to the renderer for ExtensionHostMsg_GetAppInstallState.
+IPC_MESSAGE_ROUTED2(ExtensionMsg_GetAppInstallStateResponse,
+                    std::string /* state */,
+                    int32 /* callback_id */)
+
 // Dispatch the Port.onConnect event for message channels.
 IPC_MESSAGE_ROUTED5(ExtensionMsg_DispatchOnConnect,
                     int /* target_port_id */,
@@ -401,6 +406,12 @@ IPC_MESSAGE_ROUTED4(ExtensionHostMsg_GetAppNotifyChannel,
                     int32 /* return_route_id */,
                     int32 /* callback_id */)
 
+// Sent by the renderer when a web page is checking if its app is installed.
+IPC_MESSAGE_ROUTED3(ExtensionHostMsg_GetAppInstallState,
+                    GURL /* requestor_url */,
+                    int32 /* return_route_id */,
+                    int32 /* callback_id */)
+
 // Optional Ack message sent to the browser to notify that the response to a
 // function has been processed.
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_ResponseAck,