Support touch scroll gestures in menus.

views/controls/menu/submenu_view.cc

Index: views/controls/menu/submenu_view.cc
diff --git a/views/controls/menu/submenu_view.cc b/views/controls/menu/submenu_view.cc
index 50cb44044a2bdcc1fa5860a366e55002c3654b48..1f9b38be80ee6ee890266180ce7892d4156caa6e 100644
--- a/views/controls/menu/submenu_view.cc
+++ b/views/controls/menu/submenu_view.cc
@@ -4,6 +4,9 @@
 
 #include "views/controls/menu/submenu_view.h"
 
+#include <algorithm>
+
+#include "base/compiler_specific.h"
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/gfx/canvas.h"
 #include "views/controls/menu/menu_config.h"
@@ -39,7 +42,9 @@ SubmenuView::SubmenuView(MenuItemView* parent)
       scroll_view_container_(NULL),
       max_accelerator_width_(0),
       minimum_preferred_width_(0),
-      resize_open_menu_(false) {
+      resize_open_menu_(false),
+      ALLOW_THIS_IN_INITIALIZER_LIST(
+          scroll_animator_(new ScrollAnimator(this))) {
   DCHECK(parent);
   // We'll delete ourselves, otherwise the ScrollView would delete us on close.
   set_parent_owned(false);
@@ -242,6 +247,24 @@ bool SubmenuView::OnMouseWheel(const MouseWheelEvent& e) {
   return true;
 }
 
+ui::GestureStatus SubmenuView::OnGestureEvent(const GestureEvent& e) {
+  switch (e.type()) {
+    case ui::ET_GESTURE_SCROLL_BEGIN:
+      scroll_animator_->Stop();
+      break;
+    case ui::ET_GESTURE_SCROLL_UPDATE:
+      OnScroll(0, e.delta_y());
+      break;
+    case ui::ET_GESTURE_SCROLL_END:
+      if (e.delta_y() != 0.0f)
+        scroll_animator_->Start(0, e.delta_y());
+      break;
+    default:
+      break;
+  }
+  return ui::GESTURE_STATUS_CONSUMED;
+}
+
 bool SubmenuView::IsShowing() {
   return host_ && host_->IsMenuHostVisible();
 }
@@ -395,4 +418,17 @@ gfx::Rect SubmenuView::CalculateDropIndicatorBounds(
   }
 }
 
+void SubmenuView::OnScroll(float dx, float dy) {
+  const gfx::Rect& vis_bounds = GetVisibleBounds();
+  const gfx::Rect& full_bounds = bounds();
+  int x = vis_bounds.x();
+  int y = vis_bounds.y() - static_cast<int>(dy);
+  // clamp y to [0, full_height - vis_height)
+  y = std::max(y, 0);
+  y = std::min(y, full_bounds.height() - vis_bounds.height() - 1);
+  gfx::Rect new_vis_bounds(x, y, vis_bounds.width(), vis_bounds.height());
+  if (new_vis_bounds != vis_bounds)
+    ScrollRectToVisible(new_vis_bounds);
+}
+
 }  // namespace views