DevTools: add pie chart to the paint profiler overview.

Source/devtools/front_end/components/OverviewGrid.js

Index: Source/devtools/front_end/components/OverviewGrid.js
diff --git a/Source/devtools/front_end/components/OverviewGrid.js b/Source/devtools/front_end/components/OverviewGrid.js
index d1bb842a36d4962a9fb25d473e103b313a271468..d5ae53e0c50d00794986d711f708cce034f28fb4 100644
--- a/Source/devtools/front_end/components/OverviewGrid.js
+++ b/Source/devtools/front_end/components/OverviewGrid.js
@@ -154,15 +154,15 @@ WebInspector.OverviewGrid.ResizerOffset = 3.5; // half pixel because offset valu
  * @constructor
  * @extends {WebInspector.Object}
  * @param {!Element} parentElement
- * @param {!Element} dividersLabelBarElement
+ * @param {!Element=} dividersLabelBarElement
  */
 WebInspector.OverviewGrid.Window = function(parentElement, dividersLabelBarElement)
 {
     this._parentElement = parentElement;
-    this._dividersLabelBarElement = dividersLabelBarElement;
 
     WebInspector.installDragHandle(this._parentElement, this._startWindowSelectorDragging.bind(this), this._windowSelectorDragging.bind(this), this._endWindowSelectorDragging.bind(this), "ew-resize", null);
-    WebInspector.installDragHandle(this._dividersLabelBarElement, this._startWindowDragging.bind(this), this._windowDragging.bind(this), null, "move");
+    if (dividersLabelBarElement)
+        WebInspector.installDragHandle(dividersLabelBarElement, this._startWindowDragging.bind(this), this._windowDragging.bind(this), null, "move");
 
     this.windowLeft = 0.0;
     this.windowRight = 1.0;