DevTools: introduce multitarget model listeners

LayoutTests/http/tests/inspector/inspector-test.js

 var initialize_InspectorTest = function() {
 
 var results = [];
 var resultsSynchronized = false;
 
 function consoleOutputHook(messageType)
 {
     InspectorTest.addResult(messageType + ": " + Array.prototype.slice.call(arguments, 1));
 }
 
@@ skipping 596 matching lines @@
 
 WebInspector.TempFile = InspectorTest.TempFileMock;
 
 WebInspector.targetManager.observeTargets({
     targetAdded: function(target)
     {
         if (!WebInspector.domModel)
             WebInspector.domModel = target.domModel;
         if (!WebInspector.consoleModel)
             WebInspector.consoleModel = target.consoleModel;
+        if (!WebInspector.networkManager)
+            WebInspector.networkManager = target.networkManager;
     },
 
     targetRemoved: function(target) { }
 });
 
 };  // initialize_InspectorTest
 
 var initializeCallId = 0;
 var runTestCallId = 1;
 var completeTestCallId = 2;
@@ skipping 207 matching lines @@
     evaluateInWebInspector: function(callId, script)
     {
         window.opener.postMessage(["evaluateInWebInspector", callId, script], "*");
     },
 
     display: function() { }
 }
 
 if (!window.testRunner && window.opener)
     window.testRunner = new StandaloneTestRunnerStub();