Remove a check that always evaluates to true in AppMenuModel.

Change-Id: I9ca2e8106ae2f9e35d841709137b3906d007f589
Reviewed-on: https://chromium-review.googlesource.com/c/1457433Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630166}

chrome/browser/ui/toolbar/app_menu_model.cc

@@ -244,11 +244,12 @@ AppMenuModel::AppMenuModel(ui::AcceleratorProvider* provider,
       uma_action_recorded_(false),
       provider_(provider),
       browser_(browser),
-      app_menu_icon_controller_(app_menu_icon_controller) {}
+      app_menu_icon_controller_(app_menu_icon_controller) {
+  DCHECK(browser_);
+}
 
 AppMenuModel::~AppMenuModel() {
-  if (browser_)  // Null in Cocoa tests.
-    browser_->tab_strip_model()->RemoveObserver(this);
+  browser_->tab_strip_model()->RemoveObserver(this);
 }
 
 void AppMenuModel::Init() {