Add chrome.debugger.getTargets method to discover available debug targets.

chrome/test/data/extensions/api_test/debugger/background.js

 // Copyright (c) 2011 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.
 
 var pass = chrome.test.callbackPass;
 var fail = chrome.test.callbackFail;
 
 var tabId;
 var debuggee;
 var protocolVersion = "1.0";
@@ skipping 93 matching lines @@
     var missingDebuggee = {tabId: -1};
     chrome.debugger.attach(missingDebuggee, protocolVersion,
         fail("No tab with given id " + missingDebuggee.tabId + "."));
   },
 
   function attachToExtensionWithNoSilentFlag() {
     debuggeeExtension = {extensionId: "foo"};
     chrome.debugger.attach(debuggeeExtension, protocolVersion,
         fail("Cannot attach to an extension unless " +
             "'silent-debugger-extension-api' flag is enabled."));
+  },
+
+  function createAndDiscoverTab() {
+    chrome.test.listenOnce(chrome.tabs.onUpdated, function () {
+      chrome.debugger.getTargets(function(targets) {
+        var page = targets.filter(
+            function(t) {
+              return t.type == 'page' && t.title == 'Test page';
+            })[0];
+        if (page) {
+          chrome.debugger.attach(
+              {targetId: page.id}, protocolVersion, pass());
+        } else {
+          chrome.test.fail("Cannot discover a newly created tab");
+        }
+      });
+    });
+    chrome.tabs.create({url: "inspected.html"});
+  },
+
+  function discoverExtensionWithNoSilentFlag() {
+    chrome.debugger.getTargets(function(targets) {
+      var target = targets.filter(
+          function(target) { return target.type == 'extension'})[0];
+      if (target) {
+        chrome.debugger.attach({targetId: target.id}, protocolVersion,
+            fail("Cannot attach to an extension unless " +
+                "'silent-debugger-extension-api' flag is enabled."));
+      } else {
+        chrome.test.succeed();
+      }
+    });
   }
 ]);