DevTools: zoom frames upon double click, iterate over frames using arrows.

Source/devtools/front_end/ui_lazy/OverviewGrid.js

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 368 matching lines @@
 
         // We allow actual time window to be arbitrarily small but don't want the UI window to be too small.
         var widthInPixels = width * this._parentElement.clientWidth;
         var minWidthInPixels = WebInspector.OverviewGrid.MinSelectableSize / 2;
         if (widthInPixels < minWidthInPixels) {
             var factor = minWidthInPixels / widthInPixels;
             left = ((windowRight + windowLeft) - width * factor) / 2;
             right = ((windowRight + windowLeft) + width * factor) / 2;
         }
 
+        if (windowLeft === this.windowLeft && windowRight === this.windowRight)
+            return;
+
         this.windowLeft = windowLeft;
         this._leftResizeElement.style.left = left * 100 + "%";
         this.windowRight = windowRight;
         this._rightResizeElement.style.left = right * 100 + "%";
 
         this._overviewWindowElement.style.left = left * 100 + "%";
         this._overviewWindowBordersElement.style.left = left * 100 + "%";
         this._overviewWindowElement.style.width = (right - left) * 100 + "%";
         this._overviewWindowBordersElement.style.right = (1 - right) * 100 + "%";
 
@@ skipping 95 matching lines @@
         position = Math.max(0, Math.min(position, this._width));
         if (position < this._startPosition) {
             this._windowSelector.style.left = position + "px";
             this._windowSelector.style.right = this._width - this._startPosition + "px";
         } else {
             this._windowSelector.style.left = this._startPosition + "px";
             this._windowSelector.style.right = this._width - position + "px";
         }
     }
 }