Fix task groups to always be self-consistent.

chrome/browser/task_manager/legacy_task_manager_tester.cc

Index: chrome/browser/task_manager/legacy_task_manager_tester.cc
diff --git a/chrome/browser/task_manager/legacy_task_manager_tester.cc b/chrome/browser/task_manager/legacy_task_manager_tester.cc
index b1badb1bd8a9cbe495c54e2daa0fb9954c1f7991..77e5e46c7c3bc0088aad7f850222ad385bbc0524 100644
--- a/chrome/browser/task_manager/legacy_task_manager_tester.cc
+++ b/chrome/browser/task_manager/legacy_task_manager_tester.cc
@@ -71,6 +71,13 @@ class LegacyTaskManagerTester : public task_management::TaskManagerTester,
 
   void Kill(int row) override { TaskManager::GetInstance()->KillProcess(row); }
 
+  void GetRowsGroupRange(int row, int* out_start, int* out_length) override {
+    TaskManagerModel::GroupRange group_range =
+        model_->GetGroupRangeForResource(row);
+    *out_start = group_range.first;
+    *out_length = group_range.second;
+  }
+
   // TaskManagerModelObserver:
   void OnModelChanged() override { OnResourceChange(); }
   void OnItemsChanged(int start, int length) override { OnResourceChange(); }