Disable drag-and-drop on login flow to avoid hanging.

BUG=464118
TEST=manual

Review URL: https://codereview.chromium.org/992173004

Cr-Commit-Position: refs/heads/master@{#320574}

2 files changed, 95 insertions, 0 deletions

diff --git a/ui/wm/public/scoped_drag_drop_disabler.cc b/ui/wm/public/scoped_drag_drop_disabler.cc
new file mode 100644
index 0000000..aaeb56d
--- /dev/null
+++ b/ui/wm/public/scoped_drag_drop_disabler.cc
@@ -0,0 +1,55 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/wm/public/scoped_drag_drop_disabler.h"
+
+#include "ui/aura/window.h"
+#include "ui/wm/public/drag_drop_client.h"
+
+namespace aura {
+namespace client {
+
+class NopDragDropClient : public DragDropClient {
+ public:
+  ~NopDragDropClient() override {}
+  int StartDragAndDrop(const ui::OSExchangeData& data,
+                       aura::Window* root_window,
+                       aura::Window* source_window,
+                       const gfx::Point& screen_location,
+                       int operation,
+                       ui::DragDropTypes::DragEventSource source) override {
+    return 0;
+  }
+  void DragUpdate(aura::Window* target,
+                  const ui::LocatedEvent& event) override {}
+  void Drop(aura::Window* target, const ui::LocatedEvent& event) override {}
+  void DragCancel() override {}
+  bool IsDragDropInProgress() override {
+    return false;
+  }
+};
+
+ScopedDragDropDisabler::ScopedDragDropDisabler(Window* window)
+    : window_(window),
+      old_client_(GetDragDropClient(window)),
+      new_client_(new NopDragDropClient()) {
+  SetDragDropClient(window_, new_client_.get());
+  window_->AddObserver(this);
+}
+
+ScopedDragDropDisabler::~ScopedDragDropDisabler() {
+  if (window_) {
+    window_->RemoveObserver(this);
+    SetDragDropClient(window_, old_client_);
+  }
+}
+
+void ScopedDragDropDisabler::OnWindowDestroyed(Window* window) {
+  CHECK_EQ(window_, window);
+  window_ = NULL;
+  new_client_.reset();
+}
+
+}  // namespace client
+}  // namespace aura
diff --git a/ui/wm/public/scoped_drag_drop_disabler.h b/ui/wm/public/scoped_drag_drop_disabler.h
new file mode 100644
index 0000000..4f708ee
--- /dev/null
+++ b/ui/wm/public/scoped_drag_drop_disabler.h
@@ -0,0 +1,40 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_WM_PUBLIC_SCOPED_DRAG_DROP_DISABLER_H_
+#define UI_WM_PUBLIC_SCOPED_DRAG_DROP_DISABLER_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/aura/window_observer.h"
+
+namespace aura {
+class Window;
+
+namespace client {
+class DragDropClient;
+
+// ScopedDragDropDisabler is used to temporarily replace the drag'n'drop client
+// for a window with a "no-op" client. Upon construction, it installs a new
+// client on the window, and upon destruction, it restores the previous one.
+class AURA_EXPORT ScopedDragDropDisabler : public WindowObserver {
+ public:
+  explicit ScopedDragDropDisabler(Window* window);
+  ~ScopedDragDropDisabler() override;
+
+ private:
+  // WindowObserver:
+  void OnWindowDestroyed(Window* window) override;
+
+  Window* window_;
+  DragDropClient* old_client_;
+  scoped_ptr<DragDropClient> new_client_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedDragDropDisabler);
+};
+
+}  // namespace client
+}  // namespace aura
+
+#endif  // UI_WM_PUBLIC_SCOPED_DRAG_DROP_DISABLER_H_