cros: Only preload the lock screen; do not reuse it.

chrome/browser/chromeos/login/lock/webui_screen_locker.h

Index: chrome/browser/chromeos/login/lock/webui_screen_locker.h
diff --git a/chrome/browser/chromeos/login/lock/webui_screen_locker.h b/chrome/browser/chromeos/login/lock/webui_screen_locker.h
index 2a49acd28292e8d7f4a0a1ae8c30ea6048774dc1..8b47b7afc7206c4b32f322ec3e95bb20893c7fd0 100644
--- a/chrome/browser/chromeos/login/lock/webui_screen_locker.h
+++ b/chrome/browser/chromeos/login/lock/webui_screen_locker.h
@@ -55,9 +55,9 @@ class WebUIScreenLocker : public WebUILoginView,
                           public display::DisplayObserver,
                           public content::WebContentsObserver {
  public:
-  // Returns true if the lock screen should be shared.
-  static bool ShouldShareLockScreen();
-  static void Preload();
+  // Request lock screen preload when the user is idle. Does nothing if
+  // preloading is disabled or if the preload hueristics return false.
+  static void RequestPreload();
 
   explicit WebUIScreenLocker(ScreenLocker* screen_locker);
   ~WebUIScreenLocker() override;
@@ -95,6 +95,11 @@ class WebUIScreenLocker : public WebUILoginView,
  private:
   friend class test::WebUIScreenLockerTester;
 
+  // Returns true if the lock screen should be preloaded.
+  static bool ShouldPreloadLockScreen();
+  // Helper function that creates and preloads a views::WebView.
+  static std::unique_ptr<views::WebView> DoPreload(Profile* profile);
+
   // LoginDisplay::Delegate:
   void CancelPasswordChangedFlow() override;
   void CompleteLogin(const UserContext& user_context) override;
@@ -158,6 +163,9 @@ class WebUIScreenLocker : public WebUILoginView,
   // Reset user pod and ensures that user pod is focused.
   void ResetAndFocusUserPod();
 
+  // Configuration settings.
+  WebViewSettings BuildConfigSettings();
+
   // The ScreenLocker that owns this instance.
   ScreenLocker* screen_locker_ = nullptr;