Specify the correct the parent to KeyBindingEditor

Seems that we have specified a wrong parent to KeyBindingEditor, which
had not been obvious until we switched to Qt 5, where OK/Cancel buttons
do not work because of this.

Fix #399.

BUG=#399
TEST=Manually on Qt 4.8.7 (Win), Qt 5.6.2 (Win), Qt 5.2.1 (Ubuntu 14.04)
REF_BUG=33256462
REF_CL=140696390
REF_TIME=2016-11-30T23:15:33-08:00
REF_TIME_RAW=1480576533 -0800

src/data/version/mozc_version_template.bzl

@@ -30,7 +30,7 @@
 
 MAJOR=2
 MINOR=19
-BUILD=2664
+BUILD=2665
 REVISION=102
 # This version represents the version of Mozc IME engine (converter, predictor,
 # etc.).  This version info is included both in the Mozc server and in the Mozc

src/gui/config_dialog/keybinding_editor_delegate.cc

@@ -46,10 +46,9 @@ namespace gui {
 
 class KeyBindingEditorTriggerButton : public QPushButton {
  public:
-  KeyBindingEditorTriggerButton(QWidget *parent,
-                                QWidget *modal_parent) :
+  KeyBindingEditorTriggerButton(QWidget *parent) :
       QPushButton(parent),
-      editor_(new KeyBindingEditor(modal_parent, this)) {
+      editor_(new KeyBindingEditor(parent, this)) {
     editor_->setModal(true);   // create a modal dialog
     setFocusProxy(editor_.get());
     connect(this, SIGNAL(clicked()),
@@ -65,8 +64,7 @@ class KeyBindingEditorTriggerButton : public QPushButton {
 };
 
 KeyBindingEditorDelegate::KeyBindingEditorDelegate(QObject *parent)
-    : QItemDelegate(parent),
-      modal_parent_(static_cast<QWidget *>(parent)) {}
+    : QItemDelegate(parent) {}
 
 KeyBindingEditorDelegate::~KeyBindingEditorDelegate() {}
 
@@ -75,7 +73,7 @@ QWidget *KeyBindingEditorDelegate::createEditor(
     const QStyleOptionViewItem &option,
     const QModelIndex &index) const {
   KeyBindingEditorTriggerButton *button
-      = new KeyBindingEditorTriggerButton(parent, modal_parent_);
+      = new KeyBindingEditorTriggerButton(parent);
   CHECK(button);
   connect(button->mutable_editor(), SIGNAL(accepted()),
           this, SLOT(CommitAndCloseEditor()));

src/gui/config_dialog/keybinding_editor_delegate.h

@@ -66,9 +66,6 @@ class KeyBindingEditorDelegate : public QItemDelegate {
  private slots:
   void CommitAndCloseEditor();
   void CloseEditor();
-
- private:
-  QWidget *modal_parent_;
 };
 }  // gui
 }  // mozc