Remove DISALLOW_ macro from libcef/ (see issue #3234)

Also perform related C++ cleanup:
- Use =default instead of {} for default implementations of
  constructors/destructors.
- Replace typedef with using.

libcef/browser/views/window_view.cc

@@ -39,6 +39,9 @@ class ClientViewEx : public views::ClientView {
     DCHECK(window_delegate_);
   }
 
+  ClientViewEx(const ClientViewEx&) = delete;
+  ClientViewEx& operator=(const ClientViewEx&) = delete;
+
   views::CloseRequestResult OnWindowCloseRequested() override {
     return window_delegate_->CanWidgetClose()
                ? views::CloseRequestResult::kCanClose
@@ -47,8 +50,6 @@ class ClientViewEx : public views::ClientView {
 
  private:
   CefWindowView::Delegate* window_delegate_;  // Not owned by this object.
-
-  DISALLOW_COPY_AND_ASSIGN(ClientViewEx);
 };
 
 // Extend NativeFrameView with draggable region handling.
@@ -57,6 +58,9 @@ class NativeFrameViewEx : public views::NativeFrameView {
   NativeFrameViewEx(views::Widget* widget, CefWindowView* view)
       : views::NativeFrameView(widget), widget_(widget), view_(view) {}
 
+  NativeFrameViewEx(const NativeFrameViewEx&) = delete;
+  NativeFrameViewEx& operator=(const NativeFrameViewEx&) = delete;
+
   gfx::Rect GetWindowBoundsForClientBounds(
       const gfx::Rect& client_bounds) const override {
 #if defined(OS_WIN)
@@ -93,8 +97,6 @@ class NativeFrameViewEx : public views::NativeFrameView {
   // Not owned by this object.
   views::Widget* widget_;
   CefWindowView* view_;
-
-  DISALLOW_COPY_AND_ASSIGN(NativeFrameViewEx);
 };
 
 // The area inside the frame border that can be clicked and dragged for resizing
@@ -112,6 +114,9 @@ class CaptionlessFrameView : public views::NonClientFrameView {
   CaptionlessFrameView(views::Widget* widget, CefWindowView* view)
       : widget_(widget), view_(view) {}
 
+  CaptionlessFrameView(const CaptionlessFrameView&) = delete;
+  CaptionlessFrameView& operator=(const CaptionlessFrameView&) = delete;
+
   gfx::Rect GetBoundsForClientView() const override {
     return client_view_bounds_;
   }
@@ -222,8 +227,6 @@ class CaptionlessFrameView : public views::NonClientFrameView {
 
   // The bounds of the client view, in this view's coordinates.
   gfx::Rect client_view_bounds_;
-
-  DISALLOW_COPY_AND_ASSIGN(CaptionlessFrameView);
 };
 
 bool IsWindowBorderHit(int code) {