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..021299194fcb83ea75e96e8af4660dbb9a56a6ce 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 +33,8 @@ namespace task_management {
 
 namespace {
 
+TaskManagerTableModel* g_instance_for_testing = nullptr;
+
 #if defined(OS_MACOSX)
 // Match Activity Monitor's default refresh rate.
 const int64_t kRefreshTimeMS = 2000;
@@ -270,11 +272,18 @@ TaskManagerTableModel::TaskManagerTableModel(int64_t refresh_flags,
 #else
       is_nacl_debugging_flag_enabled_(false) {
 #endif  // !defined(DISABLE_NACL)
+
+  if (!g_instance_for_testing)

[afakhry, 2016/04/28 00:03:13]

That's weird! Can that happen? Can we instantiate a new model while another one
is still being used? Seems like an error not be to ignored.

[ncarter (slow), 2016/05/02 18:33:28]

I've added a comment to g_instance_for_testing describing the assumptions.

The view is a singleton, but there's nothing that prevents the model from having
multiple instances: for example, we were debating instantiating a second model
to drive TaskManagerTesterImpl. Since this is just a testing hook, I didn't want
to impose any limits on the behavior of TaskManagerTableModel or its unittests.
Especially since the model not being a singleton is a nice attribute of the new
task manager.

+    g_instance_for_testing = this;
+
   DCHECK(delegate);
   StartUpdating();
 }
 
 TaskManagerTableModel::~TaskManagerTableModel() {
+  if (g_instance_for_testing == this)
+    g_instance_for_testing = nullptr;
+
   StopUpdating();
 }
 
@@ -804,6 +813,11 @@ 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();