DevTools: Add JSDoc for static methods, fix JSDoc types and induced errors

Source/devtools/front_end/components/TimelineGrid.js

Index: Source/devtools/front_end/components/TimelineGrid.js
diff --git a/Source/devtools/front_end/components/TimelineGrid.js b/Source/devtools/front_end/components/TimelineGrid.js
index cca4b7c74c58094cec74f7a86341c30ff92f29ca..76471534b1bd722e235308362abedc472fdf825f 100644
--- a/Source/devtools/front_end/components/TimelineGrid.js
+++ b/Source/devtools/front_end/components/TimelineGrid.js
@@ -191,8 +191,8 @@ WebInspector.TimelineGrid.prototype = {
         var dividersElementClientWidth = this._dividersElement.clientWidth;
 
         // Reuse divider elements and labels.
-        var divider = this._dividersElement.firstChild;
-        var dividerLabelBar = this._dividersLabelBarElement.firstChild;
+        var divider = /** @type {?Element} */ (this._dividersElement.firstChild);

[aandrey, 2014/06/17 11:33:54]

why this cast? looks like some other place should be fixed.

[apavlov, 2014/06/17 12:46:03]

firstChild returns {?Node}, but given the fact that we construct the DOM
manually, it must be an {?Element}. I'm not sure if the firstElementChild getter
will be semantically equivalent. We can fix this later if need be.

The same holds for other firstChild-related casts.

+        var dividerLabelBar = /** @type {?Element} */ (this._dividersLabelBarElement.firstChild);
 
         const minWidthForTitle = 60;
         var lastPosition = 0;