[jumbo] avoid ambiguities between extensions::features:: and features::

extensions/common/extension_features.h contains an extensions::features
namespace, which can be confused with chrome/common/chrome_features.h's
features namespace in jumbo builds.

Let's disambiguate these enough to get jumbo builds working again.

Followup to this CL, which uncovered the issue (but didn't cause it):
https://chromium-review.googlesource.com/c/chromium/src/+/1145630

Bug: 866170
Change-Id: Iea5cca04c3c636014eae14f987c4aecd2dfb93bc
Reviewed-on: https://chromium-review.googlesource.com/1147521Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Mostyn Bramley-Moore <mostynb@vewd.com>
Cr-Commit-Position: refs/heads/master@{#577342}

chrome/browser/ui/extensions/hosted_app_browser_controller.cc

@@ -122,7 +122,7 @@ bool HostedAppBrowserController::IsForHostedApp(const Browser* browser) {
 // static
 bool HostedAppBrowserController::IsForExperimentalHostedAppBrowser(
     const Browser* browser) {
-  return base::FeatureList::IsEnabled(features::kDesktopPWAWindowing) &&
+  return base::FeatureList::IsEnabled(::features::kDesktopPWAWindowing) &&
          IsForHostedApp(browser);
 }
 
@@ -162,7 +162,7 @@ HostedAppBrowserController::HostedAppBrowserController(Browser* browser)
       // TODO(https://crbug.com/774918): Replace once there is a more explicit
       // indicator of a Bookmark App for an installable website.
       created_for_installed_pwa_(
-          base::FeatureList::IsEnabled(features::kDesktopPWAWindowing) &&
+          base::FeatureList::IsEnabled(::features::kDesktopPWAWindowing) &&
           UrlHandlers::GetUrlHandlers(GetExtension())) {
   browser_->tab_strip_model()->AddObserver(this);
 }