DevTools: Support popover on timeline overview.

Source/devtools/front_end/ui/Popover.js

Index: Source/devtools/front_end/ui/Popover.js
diff --git a/Source/devtools/front_end/ui/Popover.js b/Source/devtools/front_end/ui/Popover.js
index 7076551ca100cd4b996a7c69d77ac24a717a5eb4..5822b9b30adba4327f3b5f7205b1fd4c815a920c 100644
--- a/Source/devtools/front_end/ui/Popover.js
+++ b/Source/devtools/front_end/ui/Popover.js
@@ -97,8 +97,8 @@ WebInspector.Popover.prototype = {
 
         // Temporarily attach in order to measure preferred dimensions.
         var preferredSize = view ? view.measurePreferredSize() : WebInspector.measurePreferredSize(this._contentElement);
-        preferredWidth = preferredWidth || preferredSize.width;
-        preferredHeight = preferredHeight || preferredSize.height;
+        this._preferredWidth = preferredWidth || preferredSize.width;
+        this._preferredHeight = preferredHeight || preferredSize.height;
 
         window.addEventListener("resize", this._hideBound, false);
         document.body.appendChild(this._containerElement);
@@ -109,7 +109,7 @@ WebInspector.Popover.prototype = {
         else
             this._contentDiv.appendChild(this._contentElement);
 
-        this._positionElement(anchor, preferredWidth, preferredHeight, arrowDirection);
+        this.positionElement(anchor, this._preferredWidth, this._preferredHeight, arrowDirection);
 
         if (this._popoverHelper) {
             this._contentDiv.addEventListener("mousemove", this._popoverHelper._killHidePopoverTimer.bind(this._popoverHelper), true);
@@ -157,11 +157,11 @@ WebInspector.Popover.prototype = {
 
     /**
      * @param {!Element|!AnchorBox} anchorElement
-     * @param {number} preferredWidth
-     * @param {number} preferredHeight
+     * @param {number=} preferredWidth
+     * @param {number=} preferredHeight
      * @param {?WebInspector.Popover.Orientation=} arrowDirection
      */
-    _positionElement: function(anchorElement, preferredWidth, preferredHeight, arrowDirection)
+    positionElement: function(anchorElement, preferredWidth, preferredHeight, arrowDirection)
     {
         const borderWidth = this._hasNoMargins ? 0 : 8;
         const scrollerWidth = this._hasFixedHeight ? 0 : 11;
@@ -169,6 +169,8 @@ WebInspector.Popover.prototype = {
         const arrowOffset = 10;
         const borderRadius = 4;
         const arrowRadius = 6;
+        preferredWidth = preferredWidth || this._preferredWidth;
+        preferredHeight = preferredHeight || this._preferredHeight;
 
         // Skinny tooltips are not pretty, their arrow location is not nice.
         preferredWidth = Math.max(preferredWidth, 50);