DevTools: use target-based model accessors only.

Source/devtools/front_end/timeline/TimelinePowerGraph.js

Index: Source/devtools/front_end/timeline/TimelinePowerGraph.js
diff --git a/Source/devtools/front_end/timeline/TimelinePowerGraph.js b/Source/devtools/front_end/timeline/TimelinePowerGraph.js
index 1e211a40d72e65f8406a210828e93baab6f813d9..dc22835c2ac7c17e437694c37dd66ac1d90f56f9 100644
--- a/Source/devtools/front_end/timeline/TimelinePowerGraph.js
+++ b/Source/devtools/front_end/timeline/TimelinePowerGraph.js
@@ -14,7 +14,7 @@ WebInspector.TimelinePowerGraph = function(delegate, model)
     WebInspector.CountersGraph.call(this, WebInspector.UIString("POWER"), delegate, model);
 
     this._counter = this.createCounter(WebInspector.UIString("Power"), WebInspector.UIString("Power: %.2f\u2009watts"), "#d00");
-    WebInspector.powerProfiler.addEventListener(WebInspector.PowerProfiler.EventTypes.PowerEventRecorded, this._onRecordAdded, this);
+    this.target().powerProfiler.addEventListener(WebInspector.PowerProfiler.EventTypes.PowerEventRecorded, this._onRecordAdded, this);
 }
 
 WebInspector.TimelinePowerGraph.prototype = {
@@ -24,7 +24,7 @@ WebInspector.TimelinePowerGraph.prototype = {
     dispose: function()
     {
         WebInspector.CountersGraph.prototype.dispose.call(this);
-        WebInspector.powerProfiler.removeEventListener(WebInspector.PowerProfiler.EventTypes.PowerEventRecorded, this._onRecordAdded, this);
+        this.target().powerProfiler.removeEventListener(WebInspector.PowerProfiler.EventTypes.PowerEventRecorded, this._onRecordAdded, this);
     },
 
     _onRecordAdded: function(event)