QtQuick: Implement an ApplicationWindowStyle stub.

This is required for qml applications to automatically use SystemPalette background color instead of a white one when launched with QT_QUICK_CONTROLS_STYLE=Breeze.
Borders etc. are not altered, this just loads the default ApplicationWindowStyle implementation.

REVIEW: 122304

qtquickcontrols/ApplicationWindowStyle.qml

@@ -0,0 +1,5 @@
+import QtQuick 2.0
+import QtQuick.Controls.Styles 1.3
+
+ApplicationWindowStyle {
+}

qtquickcontrols/Breeze.qml

@@ -6,10 +6,7 @@ ApplicationWindow {
     width: 640
     height: 300
     title: "Breeze Style Demo"
-
-    SystemPalette { id: myPalette; colorGroup: SystemPalette.Active }
-
-    color: myPalette.window
+    style: ApplicationWindowStyle{} //Commented out to see if works when QT_QUICK_CONTROLS_STYLE=Breeze is set
 
     TabView {
         id: tabView

qtquickcontrols/qmldir

@@ -1,5 +1,6 @@
 module QtQuick.Controls.Styles.Breeze
 
+ApplicationWindowStyle 1.0 ApplicationWindowStyle.qml
 BusyIndicatorStyle 1.0 BusyIndicatorStyle.qml
 ButtonStyle 1.0 ButtonStyle.qml
 CheckBoxStyle 1.0 CheckBoxStyle.qml