Fix #231; add `ViewBag` to `ViewComponent`

- update MVC sample to demonstrate use and that `ViewBag` is scoped
- nit: add a bit of padding between border and tag cloud words

samples/MvcSample.Web/Components/TagCloud.cs

@@ -37,6 +37,7 @@ namespace MvcSample.Web.Components
 
         private string[] GetTags(int count)
         {
+            @ViewBag.Title = count.ToString() + " Tags:";
             return Tags.Take(count).ToArray();
         }
     }

samples/MvcSample.Web/Views/Shared/Components/Tags/Default.cshtml

@@ -1,6 +1,7 @@
 @model string[]
 
-<div style="width: 300px; height: 300px">
+<div style="width: 300px; height: 250px; padding: 0px 10px;">
+    <h4>@ViewBag.Title</h4>
     @foreach (var tag in Model)
     {
         <span>@tag</span>

samples/MvcSample.Web/Views/Shared/MyView.cshtml

@@ -134,6 +134,7 @@
 
     <div style="float: right; border: 5px solid red;">
         @await Component.InvokeAsync("Tags", 15)
+        <p style="padding: 0px 10px;">'@ViewBag.Title' should match page heading (still)</p>
     </div>
 </div>
 

src/Microsoft.AspNet.Mvc.Core/ViewComponents/ViewComponent.cs

@@ -7,6 +7,8 @@ namespace Microsoft.AspNet.Mvc
     [ViewComponent]
     public abstract class ViewComponent
     {
+        private dynamic _viewBag;
+
         public HttpContext Context
         {
             get { return ViewContext == null ? null : ViewContext.HttpContext; }
@@ -14,6 +16,19 @@ namespace Microsoft.AspNet.Mvc
 
         public IViewComponentResultHelper Result { get; private set; }
 
+        public dynamic ViewBag
+        {
+            get
+            {
+                if (_viewBag == null)
+                {
+                    _viewBag = new DynamicViewData(() => ViewData);
+                }
+
+                return _viewBag;
+            }
+        }
+
         public ViewContext ViewContext { get; set; }
 
         public ViewDataDictionary ViewData { get; set; }