Fix not being able to select radio buttons with the arrow keys.

Restores the OnFocus > SetChecked line in RadioButton removed in
https://chromium-review.googlesource.com/c/547075, which is required
to let the user move the radio selection with the arrow keys.

Bug: 749014
Change-Id: I861f64b3abbcaac2ec762c7014e5b5e6bee8965b
Reviewed-on: https://chromium-review.googlesource.com/595231Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491132}

ui/views/controls/button/radio_button.cc

@@ -97,6 +97,11 @@ bool RadioButton::IsGroupFocusTraversable() const {
   return false;
 }
 
+void RadioButton::OnFocus() {
+  Checkbox::OnFocus();
+  SetChecked(true);
+}
+
 void RadioButton::NotifyClick(const ui::Event& event) {
   // Set the checked state to true only if we are unchecked, since we can't
   // be toggled on and off like a checkbox.

ui/views/controls/button/radio_button.h

@@ -26,6 +26,7 @@ class VIEWS_EXPORT RadioButton : public Checkbox {
   void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
   View* GetSelectedViewForGroup(int group) override;
   bool IsGroupFocusTraversable() const override;
+  void OnFocus() override;
 
   // Overridden from Button:
   void NotifyClick(const ui::Event& event) override;