MacViews: Implement Full Keyboard Access.

ui/views/controls/button/checkbox.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/button/checkbox.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 10 matching lines @@
 const char Checkbox::kViewClassName[] = "Checkbox";
 
 Checkbox::Checkbox(const base::string16& label)
     : LabelButton(NULL, label),
       checked_(false) {
   SetHorizontalAlignment(gfx::ALIGN_LEFT);
   scoped_ptr<LabelButtonBorder> button_border(new LabelButtonBorder());
   // Inset the trailing side by a couple pixels for the focus border.
   button_border->set_insets(gfx::Insets(0, 0, 0, 2));
   SetBorder(std::move(button_border));
+
+#if !defined(OS_MACOSX)

[tapted, 2016/02/12 02:56:44]

It's usually better to avoid negatives in conditions if you can neatly. I think
the SetFocusable(false) should be redundant too, so this could be

#if defined(OS_MACOSX)
SetAccessibilityFocusable(true);
#else
SetFocusable(false);
#endif

But also button.cc already has `SetAccessibilityFocusable(true);` so perhaps we
just need 

#if !defined(OS_MACOSX)
SetFocusable(false);
#endif


But!

I nicer solution might be to do something like

PlatformStyle::SetButtonStyleFocus(View* view);

replace all the current SetFocusable(true) calls with
PlatformStyle::SetButtonStyleFocus(this) and provide platform implementations in
platform_style.cc and platform_style_mac.cc. I think this is the nicest option.

[karandeepb, 2016/02/22 07:15:37]

I have added a PlatformStyle::SetControlStyleFocus instead, since all views
which represent controls(except textfields and lists) should have this focus
setting. 

   SetFocusable(true);
+#else
+  SetFocusable(false);
+  SetAccessibilityFocusable(true);
+#endif
 
   ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
 
   // Unchecked/Unfocused images.
   SetCustomImage(false, false, STATE_NORMAL,
                  *rb.GetImageSkiaNamed(IDR_CHECKBOX));
   SetCustomImage(false, false, STATE_HOVERED,
                  *rb.GetImageSkiaNamed(IDR_CHECKBOX_HOVER));
   SetCustomImage(false, false, STATE_PRESSED,
                  *rb.GetImageSkiaNamed(IDR_CHECKBOX_PRESSED));
@@ skipping 99 matching lines @@
 ui::NativeTheme::Part Checkbox::GetThemePart() const {
   return ui::NativeTheme::kCheckbox;
 }
 
 void Checkbox::GetExtraParams(ui::NativeTheme::ExtraParams* params) const {
   LabelButton::GetExtraParams(params);
   params->button.checked = checked_;
 }
 
 }  // namespace views