新增Drawer组件，使用和popover一样的zindex机制

src/core/controller/controller.drawer.js

@@ -18,7 +18,6 @@ BI.DrawerController = BI.inherit(BI.Controller, {
         this.floatLayer = {};
         this.floatContainer = {};
         this.floatOpened = {};
-        this.zindex = BI.zIndex_popover;
         this.zindexMap = {};
     },
 
@@ -41,17 +40,18 @@ BI.DrawerController = BI.inherit(BI.Controller, {
         if (!this.floatOpened[name]) {
             this.floatOpened[name] = true;
             var container = this.floatContainer[name];
-            container.element.css("zIndex", this.zindex++);
+            var zIndex = BI.Popovers._getZIndex();
+            container.element.css("zIndex", zIndex);
             this.modal && container.element.__hasZIndexMask__(this.zindexMap[name]) && container.element.__releaseZIndexMask__(this.zindexMap[name]);
-            this.zindexMap[name] = this.zindex;
+            this.zindexMap[name] = zIndex;
             if (this.modal) {
-                var mask = container.element.__buildZIndexMask__(this.zindex++);
+                var mask = container.element.__buildZIndexMask__(BI.Popovers._getZIndex());
                 mask.click(function () {
                     mask.destroy();
                     self.get(name).close();
                 });
             }
-            this.get(name).setZindex(this.zindex++);
+            this.get(name).setZindex(BI.Popovers._getZIndex());
             this.floatContainer[name].visible();
             var popover = this.get(name);
             popover.show && popover.show();

src/core/controller/controller.popover.js

@@ -48,7 +48,8 @@ BI.PopoverController = BI.inherit(BI.Controller, {
             this.floatContainer[name].visible();
             var popover = this.get(name);
             popover.show && popover.show();
-            var W = BI.Widget._renderEngine.createElement(this.options.render).width(), H = BI.Widget._renderEngine.createElement(this.options.render).height();
+            var W = BI.Widget._renderEngine.createElement(this.options.render).width(),
+                H = BI.Widget._renderEngine.createElement(this.options.render).height();
             var w = popover.element.width(), h = popover.element.height();
             var left = (W - w) / 2, top = (H - h) / 2;
             if (left < 0) {
@@ -163,5 +164,9 @@ BI.PopoverController = BI.inherit(BI.Controller, {
         this.floatOpened = {};
         this.zindexMap = {};
         return this;
+    },
+
+    _getZIndex: function () {
+        return this.zindex++;
     }
 });