DevTools: [Console] use filtering to collapse and expand console groups

Source/devtools/front_end/sdk/ConsoleModel.js

Index: Source/devtools/front_end/sdk/ConsoleModel.js
diff --git a/Source/devtools/front_end/sdk/ConsoleModel.js b/Source/devtools/front_end/sdk/ConsoleModel.js
index a3141da52c100cdd228882418f35245ec42bf2de..1736b541f477de6cccba158f00ffb8dcca7df0cb 100644
--- a/Source/devtools/front_end/sdk/ConsoleModel.js
+++ b/Source/devtools/front_end/sdk/ConsoleModel.js
@@ -258,6 +258,15 @@ WebInspector.ConsoleMessage.prototype = {
     /**
      * @return {boolean}
      */
+    isGroupStartMessage: function()
+    {
+        return this.type === WebInspector.ConsoleMessage.MessageType.StartGroup ||
+            this.type === WebInspector.ConsoleMessage.MessageType.StartGroupCollapsed;
+    },
+
+    /**
+     * @return {boolean}
+     */
     isErrorOrWarning: function()
     {
         return (this.level === WebInspector.ConsoleMessage.MessageLevel.Warning || this.level === WebInspector.ConsoleMessage.MessageLevel.Error);