Fix content script injection for cancelled loads with PlzNavigate.

extensions/common/extension_messages.h

 // Copyright 2014 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 extensions.
 // Multiply-included message file, hence no include guard.
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 603 matching lines @@
 // the sequential nature of IPCs so that the blob has already been caught.
 // This is a separate control message, so that the renderer process will send
 // an acknowledgement even if the RenderView has closed or navigated away.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_TransferBlobs,
                      std::vector<std::string> /* blob_uuids */)
 
 // Report the WebView partition ID to the WebView guest renderer process.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_SetWebViewPartitionID,
                      std::string /* webview_partition_id */)
 
+// Sent when a 204 or 205 HTTP error is encountered, only with PlzNavigate.
+IPC_MESSAGE_ROUTED0(ExtensionMsg_Set204Or205Error)

[Charlie Reis, 2016/10/31 17:05:28]

Again, I'm wondering if this should be a more general "navigation did not
commit" message, depending on if the download case matters.

[Devlin, 2016/10/31 17:24:00]

If this *does* stay here (I'll trust y'all on that), the "Error" language seems
odd to me, since 204/205s are considered successes, I thought.  Maybe just
s/Error/Status?

+
 // Messages sent from the renderer to the browser:
 
 // A renderer sends this message when an extension process starts an API
 // request. The browser will always respond with a ExtensionMsg_Response.
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_Request,
                     ExtensionHostMsg_Request_Params)
 
 // A renderer sends this message when an extension process starts an API
 // request. The browser will always respond with a ExtensionMsg_Response.
 IPC_MESSAGE_CONTROL2(ExtensionHostMsg_RequestForIOThread,
@@ skipping 263 matching lines @@
                      int64_t /* service_worker_version_id */,
                      std::string /* request_uuid */)
 
 // Asks the browser to decrement the pending activity count for
 // the worker with version id |service_worker_version_id|.
 // |request_uuid| must match the GUID of a previous request, otherwise the
 // browser process ignores the IPC.
 IPC_MESSAGE_CONTROL2(ExtensionHostMsg_DecrementServiceWorkerActivity,
                      int64_t /* service_worker_version_id */,
                      std::string /* request_uuid */)