DevTools: Make sure network and main flamechart scales are in sync.

third_party/WebKit/Source/devtools/front_end/ui_lazy/ChartViewport.js

Index: third_party/WebKit/Source/devtools/front_end/ui_lazy/ChartViewport.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui_lazy/ChartViewport.js b/third_party/WebKit/Source/devtools/front_end/ui_lazy/ChartViewport.js
index 10413d1d8024a2ab83ceaefd7ee160b3c7620975..32ee51c15af8c7e91a7a07f7f34199713a697585 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui_lazy/ChartViewport.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui_lazy/ChartViewport.js
@@ -19,6 +19,7 @@ UI.ChartViewport = class extends UI.VBox {
         this.viewportElement, this._startRangeSelection.bind(this), this._rangeSelectionDragging.bind(this),
         this._endRangeSelection.bind(this), 'text', null);
 
+    this._alwaysShowVerticalScroll = false;
     this._vScrollElement = this.contentElement.createChild('div', 'flame-chart-v-scroll');
     this._vScrollContent = this._vScrollElement.createChild('div');
     this._vScrollElement.addEventListener('scroll', this._onScroll.bind(this), false);
@@ -29,6 +30,11 @@ UI.ChartViewport = class extends UI.VBox {
     this.reset();
   }
 
+  alwaysShowVerticalScroll() {
+    this._alwaysShowVerticalScroll = true;
+    this._vScrollElement.classList.add('always-show-scrollbar');
+  }
+
   /**
    * @return {boolean}
    */
@@ -48,7 +54,7 @@ UI.ChartViewport = class extends UI.VBox {
    * @private
    */
   _updateScrollBar() {
-    var showScroll = this._totalHeight > this._offsetHeight;
+    const showScroll = this._alwaysShowVerticalScroll || this._totalHeight > this._offsetHeight;
     if (this._vScrollElement.classList.contains('hidden') !== showScroll)
       return;
     this._vScrollElement.classList.toggle('hidden', !showScroll);