Make old task manager tests work against new task manager.

chrome/browser/ui/task_manager/task_manager_table_model.cc

Index: chrome/browser/ui/task_manager/task_manager_table_model.cc
diff --git a/chrome/browser/ui/task_manager/task_manager_table_model.cc b/chrome/browser/ui/task_manager/task_manager_table_model.cc
index 75bf306bc78a4b294667f23dd19e53bb1f52a327..3e33451ce51f1ce6e854ca711043f0794d02c523 100644
--- a/chrome/browser/ui/task_manager/task_manager_table_model.cc
+++ b/chrome/browser/ui/task_manager/task_manager_table_model.cc
@@ -33,6 +33,11 @@ namespace task_management {
 
 namespace {
 
+// Captures the first instance of TaskManagerTableModel, for use in
+// browsertests. Nothing prevents other TaskManagerTableModel instances, but in
+// practice this will be model driving the visible task manager dialog.

[afakhry, 2016/05/02 18:58:17]

... will be 'the' model driving ...

[ncarter (slow), 2016/05/02 23:09:57]

Done.

+TaskManagerTableModel* g_instance_for_testing = nullptr;
+
 #if defined(OS_MACOSX)
 // Match Activity Monitor's default refresh rate.
 const int64_t kRefreshTimeMS = 2000;
@@ -270,11 +275,18 @@ TaskManagerTableModel::TaskManagerTableModel(int64_t refresh_flags,
 #else
       is_nacl_debugging_flag_enabled_(false) {
 #endif  // !defined(DISABLE_NACL)
+
+  if (!g_instance_for_testing)
+    g_instance_for_testing = this;
+
   DCHECK(delegate);
   StartUpdating();
 }
 
 TaskManagerTableModel::~TaskManagerTableModel() {
+  if (g_instance_for_testing == this)
+    g_instance_for_testing = nullptr;
+
   StopUpdating();
 }
 
@@ -804,6 +816,11 @@ void TaskManagerTableModel::ToggleColumnVisibility(int column_id) {
   UpdateRefreshTypes(column_id, new_visibility);
 }
 
+// static
+TaskManagerTableModel* TaskManagerTableModel::GetInstanceForTesting() {
+  return g_instance_for_testing;
+}
+
 void TaskManagerTableModel::StartUpdating() {
   TaskManagerInterface::GetTaskManager()->AddObserver(this);
   tasks_ = observed_task_manager()->GetTaskIdsList();