Add DCHECKs for the touch selection menu runner singleton

This is to ensure that there exists at most one instance of the menu
runner simultaneously. This fix is now possible because of the
ViewsDelegate refactoring.

BUG=399721,492991

Review URL: https://codereview.chromium.org/1173083002

Cr-Commit-Position: refs/heads/master@{#333747}

1 files changed, 4 insertions, 5 deletions

diff --git a/ui/touch_selection/touch_selection_menu_runner.cc b/ui/touch_selection/touch_selection_menu_runner.cc
index 860a24b..bf70874 100644
--- a/ui/touch_selection/touch_selection_menu_runner.cc
+++ b/ui/touch_selection/touch_selection_menu_runner.cc
@@ -4,6 +4,8 @@
 
 #include "ui/touch_selection/touch_selection_menu_runner.h"
 
+#include "base/logging.h"
+
 namespace ui {
 namespace {
 
@@ -12,6 +14,7 @@ TouchSelectionMenuRunner* g_touch_selection_menu_runner = nullptr;
 }  // namespace
 
 TouchSelectionMenuRunner::~TouchSelectionMenuRunner() {
+  DCHECK_EQ(this, g_touch_selection_menu_runner);
   g_touch_selection_menu_runner = nullptr;
 }
 
@@ -20,11 +23,7 @@ TouchSelectionMenuRunner* TouchSelectionMenuRunner::GetInstance() {
 }
 
 TouchSelectionMenuRunner::TouchSelectionMenuRunner() {
-  // TODO(mohsen): Ideally we should DCHECK that |g_touch_selection_menu_runner|
-  // is not set here, in order to make sure we don't create multiple menu
-  // runners accidentally. Currently, this is not possible because we can have
-  // multiple ViewsDelegate's at the same time which should not happen. See
-  // crbug.com/492991.
+  DCHECK(!g_touch_selection_menu_runner);
   g_touch_selection_menu_runner = this;
 }