Document Browser::tab_strip_model() is never nullptr.

Delete code that assume it can be.

Change-Id: I2e2344d4c04ff957cf403698bdfa17bffdd602b6
Reviewed-on: https://chromium-review.googlesource.com/c/1457431Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630172}

chrome/browser/extensions/extension_tab_util.cc

@@ -759,7 +759,7 @@ bool ExtensionTabUtil::OpenOptionsPage(const Extension* extension,
 
 // static
 bool ExtensionTabUtil::BrowserSupportsTabs(Browser* browser) {
-  return browser && browser->tab_strip_model() && !browser->is_devtools();
+  return browser && !browser->is_devtools();
 }
 
 }  // namespace extensions

chrome/browser/ui/browser.cc

@@ -386,8 +386,9 @@ Browser::Browser(const CreateParams& params)
     : extension_registry_observer_(this),
       type_(params.type),
       profile_(params.profile),
-      window_(NULL),
-      tab_strip_model_delegate_(new chrome::BrowserTabStripModelDelegate(this)),
+      window_(nullptr),
+      tab_strip_model_delegate_(
+          std::make_unique<chrome::BrowserTabStripModelDelegate>(this)),
       tab_strip_model_(
           std::make_unique<TabStripModel>(tab_strip_model_delegate_.get(),
                                           params.profile)),

chrome/browser/ui/browser.h

@@ -284,7 +284,10 @@ class Browser : public TabStripModelObserver,
     location_bar_model->swap(location_bar_model_);
   }
 #endif
+
+  // Never nullptr.
   TabStripModel* tab_strip_model() const { return tab_strip_model_.get(); }
+
   chrome::BrowserCommandController* command_controller() {
     return command_controller_.get();
   }
@@ -966,8 +969,8 @@ class Browser : public TabStripModelObserver,
   // This Browser's window.
   BrowserWindow* window_;
 
-  std::unique_ptr<TabStripModelDelegate> tab_strip_model_delegate_;
-  std::unique_ptr<TabStripModel> tab_strip_model_;
+  std::unique_ptr<TabStripModelDelegate> const tab_strip_model_delegate_;
+  std::unique_ptr<TabStripModel> const tab_strip_model_;
 
   // The application name that is also the name of the window to the shell.
   // This name should be set when:

chrome/browser/ui/toolbar/app_menu_model.cc

@@ -118,8 +118,6 @@ base::string16 GetUpgradeDialogMenuItemName() {
 // Returns the appropriate menu label for the IDC_INSTALL_PWA command if
 // available.
 base::Optional<base::string16> GetInstallPWAAppMenuItemName(Browser* browser) {
-  if (!browser->tab_strip_model())
-    return base::nullopt;
   WebContents* web_contents =
       browser->tab_strip_model()->GetActiveWebContents();
   if (!web_contents)
@@ -891,14 +889,11 @@ void AppMenuModel::CreateZoomMenu() {
 }
 
 void AppMenuModel::UpdateZoomControls() {
-  int zoom_percent = 100;
-  if (browser_->tab_strip_model() &&
-      browser_->tab_strip_model()->GetActiveWebContents()) {
-    zoom_percent = zoom::ZoomController::FromWebContents(
-                       browser_->tab_strip_model()->GetActiveWebContents())
-                       ->GetZoomPercent();
-  }
-  zoom_label_ = base::FormatPercent(zoom_percent);
+  WebContents* contents = browser_->tab_strip_model()->GetActiveWebContents();
+  zoom_label_ = base::FormatPercent(
+      contents
+          ? zoom::ZoomController::FromWebContents(contents)->GetZoomPercent()
+          : 100);
 }
 
 bool AppMenuModel::ShouldShowNewIncognitoWindowMenuItem() {