Add frameId to MessageSender (extension messaging API)

extensions/common/api/runtime.json

Index: extensions/common/api/runtime.json
diff --git a/extensions/common/api/runtime.json b/extensions/common/api/runtime.json
index 8a8822c0ed4fafc98d3a6bd92279208bd8b4b62f..009769f8fc8bebfbaf995a83f492f6b20b06b7ca 100644
--- a/extensions/common/api/runtime.json
+++ b/extensions/common/api/runtime.json
@@ -36,6 +36,7 @@
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
           "tab": {"$ref": "tabs.Tab", "optional": true, "description": "The $(ref:tabs.Tab) which opened the connection, if any. This property will <strong>only</strong> be present when the connection was opened from a tab (including content scripts), and <strong>only</strong> if the receiver is an extension, not an app.", "extension_types": ["extension", "legacy_packaged_app"]},
+          "frameId": {"type": "integer", "optional": true, "description": "The <a href='webNavigation#frame_ids'>frame</a> that opened the connection. 0 for top-level frames, positive for child frames. This will only be set when <code>tab</code> is set.", "extension_types": ["extension", "legacy_packaged_app"]},
           "id": {"type": "string", "optional": true, "description": "The ID of the extension or app that opened the connection, if any."},
           "url": {"type": "string", "optional": true, "description": "The URL of the page or frame that opened the connection. If the sender is in an iframe, it will be iframe's URL not the URL of the page which hosts it."},
           "tlsChannelId": {"type": "string", "optional": true, "description": "The TLS channel ID of the page or frame that opened the connection, if requested by the extension or app, and if available."}