refactor: rename the atom directory to shell

shell/browser/ui/cocoa/root_view_mac.mm

@@ -0,0 +1,32 @@
+// Copyright (c) 2018 GitHub, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include "atom/browser/ui/cocoa/root_view_mac.h"
+
+#include "atom/browser/native_window.h"
+
+namespace atom {
+
+RootViewMac::RootViewMac(NativeWindow* window) : window_(window) {
+  set_owned_by_client();
+}
+
+RootViewMac::~RootViewMac() {}
+
+void RootViewMac::Layout() {
+  if (!window_->content_view())  // Not ready yet.
+    return;
+
+  window_->content_view()->SetBoundsRect(gfx::Rect(gfx::Point(), size()));
+}
+
+gfx::Size RootViewMac::GetMinimumSize() const {
+  return window_->GetMinimumSize();
+}
+
+gfx::Size RootViewMac::GetMaximumSize() const {
+  return window_->GetMaximumSize();
+}
+
+}  // namespace atom