Add a unit test for the experimental app list.

ui/app_list/views/start_page_view.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/app_list/views/start_page_view.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/app_list/app_list_constants.h"
 #include "ui/app_list/app_list_item.h"
@@ skipping 76 matching lines @@
   // The view containing the start page WebContents and the BarPlaceholder.
   AddChildView(instant_container_);
   views::BoxLayout* instant_layout_manager = new views::BoxLayout(
       views::BoxLayout::kVertical, 0, 0, kInstantContainerSpacing);
   instant_layout_manager->set_main_axis_alignment(
       views::BoxLayout::MAIN_AXIS_ALIGNMENT_END);
   instant_container_->SetLayoutManager(instant_layout_manager);
 
   content::WebContents* start_page_web_contents =
       view_delegate->GetStartPageContents();
-  views::WebView* web_view =
-      new views::WebView(start_page_web_contents->GetBrowserContext());
+  views::WebView* web_view = new views::WebView(
+      start_page_web_contents ? start_page_web_contents->GetBrowserContext()
+                              : NULL);
   web_view->SetPreferredSize(gfx::Size(kWebViewWidth, kWebViewHeight));
   web_view->SetWebContents(start_page_web_contents);
 
   instant_container_->AddChildView(web_view);
   instant_container_->AddChildView(new BarPlaceholderButton(this));
 
   // The view containing the start page tiles.
   AddChildView(tiles_container_);
   views::BoxLayout* tiles_layout_manager =
       new views::BoxLayout(views::BoxLayout::kHorizontal, 0, 0, kTileSpacing);
@@ skipping 34 matching lines @@
                                   const ui::Event& event) {
   app_list_main_view_->OnStartPageSearchButtonPressed();
   instant_container_->SetVisible(false);
 }
 
 void StartPageView::OnProfilesChanged() {
   Reset();
 }
 
 }  // namespace app_list