cefclient: win: Support window state restore (see issue #3359)

The cefclient sample app on Windows will persist window state across application
restart if run with cache_path and persist_user_references enabled.

To test:
1. Run `cefclient --cache-path=/path/to/cache --persist-user-preferences`
2. Move or resize the window, maximize, minimize, etc.
3. Exit cefclient.
4. Run cefclient again with the same arguments. The previous window state will
   be restored.

tests/cefclient/browser/root_window_win.h

@@ -50,6 +50,11 @@ class RootWindowWin : public RootWindow, public BrowserWindow::Delegate {
   bool WithExtension() const override;
 
  private:
+  void ContinueInitOnUIThread(std::unique_ptr<RootWindowConfig> config,
+                              const CefBrowserSettings& settings);
+  void ContinueInitOnMainThread(std::unique_ptr<RootWindowConfig> config,
+                                const CefBrowserSettings& settings);
+
   void CreateBrowserWindow(const std::string& startup_url);
   void CreateRootWindow(const CefBrowserSettings& settings,
                         bool initially_hidden);
@@ -109,54 +114,57 @@ class RootWindowWin : public RootWindow, public BrowserWindow::Delegate {
 
   void NotifyDestroyedIfDone();
 
+  static void SaveWindowRestoreOnUIThread(const WINDOWPLACEMENT& placement);
+
   // After initialization all members are only accessed on the main thread.
   // Members set during initialization.
-  bool with_controls_;
-  bool always_on_top_;
-  bool with_osr_;
-  bool with_extension_;
-  bool is_popup_;
-  RECT start_rect_;
+  bool with_controls_ = false;
+  bool always_on_top_ = false;
+  bool with_osr_ = false;
+  bool with_extension_ = false;
+  bool is_popup_ = false;
+  CefRect initial_bounds_;
+  cef_show_state_t initial_show_state_ = CEF_SHOW_STATE_NORMAL;
   std::unique_ptr<BrowserWindow> browser_window_;
   CefBrowserSettings browser_settings_;
-  bool initialized_;
+  bool initialized_ = false;
 
   // Main window.
-  HWND hwnd_;
+  HWND hwnd_ = nullptr;
 
   // Draggable region.
-  HRGN draggable_region_;
+  HRGN draggable_region_ = nullptr;
 
   // Font for buttons and text fields.
-  HFONT font_;
-  int font_height_;
+  HFONT font_ = nullptr;
+  int font_height_ = 0;
 
   // Buttons.
-  HWND back_hwnd_;
-  HWND forward_hwnd_;
-  HWND reload_hwnd_;
-  HWND stop_hwnd_;
+  HWND back_hwnd_ = nullptr;
+  HWND forward_hwnd_ = nullptr;
+  HWND reload_hwnd_ = nullptr;
+  HWND stop_hwnd_ = nullptr;
 
   // URL text field.
-  HWND edit_hwnd_;
-  WNDPROC edit_wndproc_old_;
+  HWND edit_hwnd_ = nullptr;
+  WNDPROC edit_wndproc_old_ = nullptr;
 
   // Find dialog.
-  HWND find_hwnd_;
-  UINT find_message_id_;
-  WNDPROC find_wndproc_old_;
+  HWND find_hwnd_ = nullptr;
+  UINT find_message_id_ = 0;
+  WNDPROC find_wndproc_old_ = nullptr;
 
   // Find dialog state.
-  FINDREPLACE find_state_;
-  WCHAR find_buff_[80];
+  FINDREPLACE find_state_ = {0};
+  WCHAR find_buff_[80] = {0};
   std::wstring find_what_last_;
-  bool find_next_;
-  bool find_match_case_last_;
+  bool find_next_ = false;
+  bool find_match_case_last_ = false;
 
-  bool window_destroyed_;
-  bool browser_destroyed_;
+  bool window_destroyed_ = false;
+  bool browser_destroyed_ = false;
 
-  bool called_enable_non_client_dpi_scaling_;
+  bool called_enable_non_client_dpi_scaling_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowWin);
 };