[Devtools] Prepare network log view for grouping support

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

Index: third_party/WebKit/Source/devtools/front_end/ui_lazy/ViewportDataGrid.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui_lazy/ViewportDataGrid.js b/third_party/WebKit/Source/devtools/front_end/ui_lazy/ViewportDataGrid.js
index d75c69b911fb04057c98b33f68d675f086410e68..ec3b5c89214bef6384252fd81fe4f539eed4ac08 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui_lazy/ViewportDataGrid.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui_lazy/ViewportDataGrid.js
@@ -122,7 +122,7 @@ UI.ViewportDataGrid = class extends UI.DataGrid {
    * @return {{topPadding: number, bottomPadding: number, contentHeight: number, visibleNodes: !Array.<!UI.ViewportDataGridNode>, offset: number}}
    */
   _calculateVisibleNodes(clientHeight, scrollTop) {
-    var nodes = this.rootNode().flattenChildren();
+    var nodes = (/** @type {!UI.ViewportDataGridNode} */ (this.rootNode())).flattenChildren();
     if (this._inline)
       return {topPadding: 0, bottomPadding: 0, contentHeight: 0, visibleNodes: nodes, offset: 0};
 
@@ -156,7 +156,7 @@ UI.ViewportDataGrid = class extends UI.DataGrid {
    * @return {number}
    */
   _contentHeight() {
-    var nodes = this.rootNode().flattenChildren();
+    var nodes = (/** @type {!UI.ViewportDataGridNode} */ (this.rootNode())).flattenChildren();
     var result = 0;
     for (var i = 0, size = nodes.length; i < size; ++i)
       result += nodes[i].nodeSelfHeight();
@@ -232,7 +232,7 @@ UI.ViewportDataGrid = class extends UI.DataGrid {
    * @param {!UI.ViewportDataGridNode} node
    */
   _revealViewportNode(node) {
-    var nodes = this.rootNode().flattenChildren();
+    var nodes = (/** @type {!UI.ViewportDataGridNode} */ (this.rootNode())).flattenChildren();
     var index = nodes.indexOf(node);
     if (index === -1)
       return;
@@ -270,6 +270,8 @@ UI.ViewportDataGridNode = class extends UI.DataGridNode {
     this._stale = false;
     /** @type {?Array<!UI.ViewportDataGridNode>} */
     this._flatNodes = null;
+    /** @type {?Array<!UI.ViewportDataGridNode>} */
+    this._flatVisibleNodes = null;
   }
 
   /**
@@ -292,6 +294,7 @@ UI.ViewportDataGridNode = class extends UI.DataGridNode {
   }
 
   _clearFlatNodes() {
+    this._flatVisibleNodes = null;
     this._flatNodes = null;
     var parent = /** @type {!UI.ViewportDataGridNode} */ (this.parent);
     if (parent)
@@ -299,12 +302,15 @@ UI.ViewportDataGridNode = class extends UI.DataGridNode {
   }
 
   /**
+   * @param {boolean=} includeCollapsed
    * @return {!Array<!UI.ViewportDataGridNode>}
    */
-  flattenChildren() {
-    if (this._flatNodes)
+  flattenChildren(includeCollapsed) {
+    if (!includeCollapsed && this._flatVisibleNodes)
+      return this._flatVisibleNodes;
+    if (includeCollapsed && this._flatNodes)
       return this._flatNodes;
-    var flatNodes = [];
+    var nodesList = [];
     var children = [this.children];
     var counters = [0];
     var depth = 0;
@@ -314,17 +320,19 @@ UI.ViewportDataGridNode = class extends UI.DataGridNode {
         depth--;
         continue;
       }
-      flatNodes.push(node);
+      nodesList.push(node);
       node.setDepth(depth);
-      if (node._expanded && node.children.length) {
+      if ((includeCollapsed || node._expanded) && node.children.length) {
         depth++;
         children[depth] = node.children;
         counters[depth] = 0;
       }
     }
-
-    this._flatNodes = flatNodes;
-    return flatNodes;
+    if (includeCollapsed)
+      this._flatNodes = nodesList;
+    else
+      this._flatVisibleNodes = nodesList;
+    return nodesList;
   }
 
   /**