Fix content script injection for cancelled loads with PlzNavigate.

extensions/common/extension_messages.h

Index: extensions/common/extension_messages.h
diff --git a/extensions/common/extension_messages.h b/extensions/common/extension_messages.h
index 55f72aa1e88a96630e42386ed5a8e59d2adc527e..24017359adb3cf0aba85fe56a47ac7ec5733579f 100644
--- a/extensions/common/extension_messages.h
+++ b/extensions/common/extension_messages.h
@@ -621,6 +621,9 @@ IPC_MESSAGE_CONTROL1(ExtensionMsg_TransferBlobs,
 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