Make IsTriggerableEvent take Event objects and use it to verify whether tap events should trigger.

ui/views/controls/button/button_dropdown.cc

Index: ui/views/controls/button/button_dropdown.cc
diff --git a/ui/views/controls/button/button_dropdown.cc b/ui/views/controls/button/button_dropdown.cc
index 3fcfb6140047da7df0e3cd97724a8d91acdf5e0f..3a0e8668fa1ed2112d75e240061a42c1a771847e 100644
--- a/ui/views/controls/button/button_dropdown.cc
+++ b/ui/views/controls/button/button_dropdown.cc
@@ -123,11 +123,13 @@ void ButtonDropDown::GetAccessibleState(ui::AccessibleViewState* state) {
   state->state = ui::AccessibilityTypes::STATE_HASPOPUP;
 }
 
-bool ButtonDropDown::ShouldEnterPushedState(const MouseEvent& event) {
-  // Enter PUSHED state on press with Left or Right mouse button. Remain
-  // in this state while the context menu is open.
-  return ((ui::EF_LEFT_MOUSE_BUTTON |
-      ui::EF_RIGHT_MOUSE_BUTTON) & event.flags()) != 0;
+bool ButtonDropDown::ShouldEnterPushedState(const Event& event) {
+  // Enter PUSHED state on press with Left or Right mouse button or on taps.
+  // Remain in this state while the context menu is open.
+  return event.type() == ui::ET_GESTURE_TAP ||
+         event.type() == ui::ET_GESTURE_TAP_DOWN ||
+         (event.IsMouseEvent() && ((ui::EF_LEFT_MOUSE_BUTTON |
+             ui::EF_RIGHT_MOUSE_BUTTON) & event.flags()) != 0);
 }
 
 void ButtonDropDown::ShowDropDownMenu(gfx::NativeView window) {