[Extensions Bindings] Request JS execution from messaging bindings

extensions/renderer/resources/messaging.js

Index: extensions/renderer/resources/messaging.js
diff --git a/extensions/renderer/resources/messaging.js b/extensions/renderer/resources/messaging.js
index 86c110b1de860cc661478dd05a7b64bea4081088..90aa66b6949fcad39198cf07908eb4264e2f7721 100644
--- a/extensions/renderer/resources/messaging.js
+++ b/extensions/renderer/resources/messaging.js
@@ -247,6 +247,33 @@
                              targetExtensionId,
                              sourceUrl,
                              tlsChannelId) {
+    var usedPort = dispatchOnConnectImpl(portId, channelName, sourceTab,
+                                         sourceFrameId, guestProcessId,
+                                         guestRenderFrameRoutingId,
+                                         sourceExtensionId, targetExtensionId,
+                                         sourceUrl, tlsChannelId);
+    if (!usedPort) {

[lazyboy, 2017/06/05 18:18:33]

nit: isPortUsed (usedPort var might be misleading to mean that it is the used
port).

[Devlin, 2017/06/09 20:18:02]

Good point; changed to wasPortUsed.

+      // Since the JS to dispatch the connect event can (in rare cases) be
+      // executed asynchronously from when we check if there are associated
+      // listeners in the native code, it's possible that the listeners have
+      // since been removed. If that's the case (though unlikely), remove the
+      // port.
+      messagingNatives.CloseChannel(portId, false);

[lazyboy, 2017/06/05 18:18:33]

nit: false /* force_close */

[Devlin, 2017/06/09 20:18:02]

Done.

+    }
+  }
+
+  // Helper function to dispatchOnConnect that returns true if the new port
+  // was used.
+  function dispatchOnConnectImpl(portId,
+                                 channelName,
+                                 sourceTab,
+                                 sourceFrameId,
+                                 guestProcessId,
+                                 guestRenderFrameRoutingId,
+                                 sourceExtensionId,
+                                 targetExtensionId,
+                                 sourceUrl,
+                                 tlsChannelId) {
     // Only create a new Port if someone is actually listening for a connection.
     // In addition to being an optimization, this also fixes a bug where if 2
     // channels were opened to and from the same process, closing one would