Chrome extension to get console messages upon test failures. Unlike the

tools/testing/extensions/chrome/ConsoleCollector/background.js

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// This is the background window. It can access the necessary APIs to get
+// at the console messages. It can only communicate with the content
+// window through message passing.
+//
+// There is no way to query the console messages, as such, but we can
+// set up a handler that is called when there are console messages. This 
+// will be called with any console messages already present, so it can be set
+// up after the fact. However, if there are no messages it won't be called.
+// To handle the end of the messages (or no messages) we have to use a timer
+// that can fire when the handler has been idle for a while.
+
+var version = "1.0";
+var messages = []; // An array that we can put messages in.
+var debuggee; // An object that identifies the browser tab we are talking to.
+var callback; // For passing back the response to the content window.
+var timer; // To time out if no messages are available.
+
+function allDone() {
+  callback(messages); // Send back the messages we obtained.
+  // Turn off console listening and debugging.
+  chrome.debugger.sendCommand(debuggee, "Console.disable", {}, function() { });
+  chrome.debugger.detach(debuggee, function() {});
+}
+
+function onEvent(debuggeeId, method, params) {
+  clearTimeout(timer); // Reset the timeout.
+  var tabId = debuggeeId.tabId;
+  if (method == "Console.messageAdded") {
+    var msg = params.message;
+    // More fields are available if we want them later. See
+    // https://developers.google.com/chrome-developer-tools/docs/\
+    //     protocol/1.0/console#type-ConsoleMessage
+    messages.push({"source":msg.url, "line": msg.line,
+        "category":msg.source, "message":msg.text });
+  }
+  timer = setTimeout(allDone, 1000);
+}
+
+// Set up the general handler for debug events.
+chrome.debugger.onEvent.addListener(onEvent);
+
+// Handle requests sent by the content script.
+function onRequest(request, sender, sendResponse) {
+  if (request.command == "getMessages") {
+    callback = sendResponse; // Save the callback for later.
+    // Get the window and tab we are talking to.
+    chrome.windows.getCurrent(function(win) {
+      chrome.tabs.getSelected(win.id, function(tab) {
+        debuggeeId = {tabId:tab.id};
+        // Attach the debugger to the tab.
+        chrome.debugger.attach(debuggeeId, version, function() {
+          if (chrome.extension.lastError) {
+            // Attach failed; send an empty response.
+            callback([]);
+          } else {
+            // Turn on console message event handling.
+            chrome.debugger.sendCommand(debuggeeId, "Console.enable", {},
+              function() {});
+            timer = setTimeout(allDone, 1000);
+          }
+        });
+      });
+    });
+  }
+}
+
+// Listen for the content script to send a message to the background page.
+chrome.extension.onRequest.addListener(onRequest);
+