[MacViews] Show combobox menu popup at mouse press

ui/views/controls/combobox/combobox.cc

 // Copyright (c) 2012 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/views/controls/combobox/combobox.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 92 matching lines @@
   return bounds;
 }
 
 // The transparent button which holds a button state but is not rendered.
 class TransparentButton : public CustomButton {
  public:
   TransparentButton(ButtonListener* listener)
       : CustomButton(listener) {
     SetAnimationDuration(LabelButton::kHoverAnimationDurationMs);
     SetFocusBehavior(FocusBehavior::NEVER);
+    set_notify_action(NOTIFY_ON_PRESS);

[tapted, 2016/06/16 00:05:13]

We need to restrict this just to Mac - I think the way to go about it is to add

CustomButton::NotifyAction PlatformStyle::kMenuActivationAction =
CustomButton::NOTIFY_ON_PRESS;

in platform_style_mac.mm

(and = CustomButton::NOTIFY_ON_RELEASE in platform_style.cc within the !mac
guards)

[spqchan, 2016/06/22 02:16:38]

Done.

   }
   ~TransparentButton() override {}
 
   bool OnMousePressed(const ui::MouseEvent& mouse_event) override {
     parent()->RequestFocus();

[tapted, 2016/06/16 00:05:13]

This actually isn't needed, CustomButton has a set_request_focus_on_press(bool)
method which TransparentButton can call in the constructor.

Conveniently, that setter is disabled on Mac - and that's exactly what we want,
since activating a native combobox doesn't transfer focus to the combobox
control.

So I think we can get rid of the OnMousePressed override completely (regardless
of platform) by adding that set_request_focus_on_press call

(make sure you say something about this in the CL description, since it's
subtle)

[spqchan, 2016/06/22 02:16:38]

Done.

+    CustomButton::OnMousePressed(mouse_event);
     return true;
   }
 
   double GetAnimationValue() const {
     return hover_animation().GetCurrentValue();
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(TransparentButton);
 };
@@ skipping 769 matching lines @@
 
 int Combobox::GetArrowContainerWidth() const {
   const int kNormalPadding = 7;
   int padding = style_ == STYLE_NORMAL
                     ? kNormalPadding * 2
                     : kActionLeftPadding + kActionRightPadding;
   return ArrowSize().width() + padding;
 }
 
 }  // namespace views