Devtools: Support disabling and enabling of debugger in TargetBreakpoints

LayoutTests/inspector/sources/debugger/breakpoint-manager.js

 var initialize_BreakpointManagerTest = function() {
 
 InspectorTest.uiSourceCodes = {};
 
 InspectorTest.initializeDefaultMappingOnTarget = function (target) {
     var defaultMapping = {
         rawLocationToUILocation: function(rawLocation)
         {
             return InspectorTest.uiSourceCodes[rawLocation.scriptId].uiLocation(rawLocation.lineNumber, 0);
         },
@@ skipping 23 matching lines @@
     this._sourceMapping = sourceMapping;
     this._breakpoints = {};
 }
 
 InspectorTest.DebuggerModelMock.prototype = {
     target: function()
     {
         return this._target;
     },
 
+    debuggerEnabled: function()
+    {
+        return true;
+    },
+
     _addScript: function(scriptId, url)
     {
         this._scripts[scriptId] = new WebInspector.Script(this._target, scriptId, url);
         this._scripts[scriptId].pushSourceMapping(this._sourceMapping);
     },
 
     _scriptForURL: function(url)
     {
         for (var scriptId in this._scripts) {
             var script = this._scripts[scriptId];
@@ skipping 245 matching lines @@
     {
         InspectorTest.dumpBreakpointLocations(breakpointManager);
         next();
     }
 
     InspectorTest.dumpBreakpointLocations(breakpointManager);
     InspectorTest.resetBreakpointManager(breakpointManager, finish);
 }
 
 }