[DevTools] Minor tweak in popover positioning.

Source/devtools/front_end/Popover.js

 /*
  * Copyright (C) 2009 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 164 matching lines @@
                 newElementPosition.height = anchorBox.y - borderRadius * 2 - arrowHeight;
                 if (this._hasFixedHeight && newElementPosition.height < preferredHeight) {
                     newElementPosition.y = borderRadius;
                     newElementPosition.height = preferredHeight;
                 }
             }
             verticalAlignment = WebInspector.Popover.Orientation.Bottom;
         } else {
             // Positioning below the anchor.
             newElementPosition.y = anchorBox.y + anchorBox.height + arrowHeight;
-            if ((newElementPosition.y + newElementPosition.height + arrowHeight - borderWidth >= totalHeight) && (arrowDirection !== WebInspector.Popover.Orientation.Top)) {
-                newElementPosition.height = totalHeight - anchorBox.y - anchorBox.height - borderRadius * 2 - arrowHeight;
+            if ((newElementPosition.y + newElementPosition.height + borderRadius >= totalHeight) && (arrowDirection !== WebInspector.Popover.Orientation.Top)) {
+                newElementPosition.height = totalHeight - borderRadius - newElementPosition.y;
                 if (this._hasFixedHeight && newElementPosition.height < preferredHeight) {
                     newElementPosition.y = totalHeight - preferredHeight - borderRadius;
                     newElementPosition.height = preferredHeight;
                 }
             }
             // Align arrow.
             verticalAlignment = WebInspector.Popover.Orientation.Top;
         }
 
         var horizontalAlignment;
@@ skipping 189 matching lines @@
             this._resetHoverTimer();
         }
     }
 }
 
 /** @enum {string} */
 WebInspector.Popover.Orientation = {
     Top: "top",
     Bottom: "bottom"
 }