Add chrome.app.window API tests for items shown in shelf

chrome/browser/apps/app_browsertest_util.h

Index: chrome/browser/apps/app_browsertest_util.h
diff --git a/chrome/browser/apps/app_browsertest_util.h b/chrome/browser/apps/app_browsertest_util.h
index 2e129b0b01c39e261147bf303777c81d3d59f3e8..94c8bc6775ed009482685b73c0cb3a8b698a98fb 100644
--- a/chrome/browser/apps/app_browsertest_util.h
+++ b/chrome/browser/apps/app_browsertest_util.h
@@ -124,6 +124,9 @@ class PlatformAppBrowserTest : public ExtensionApiTest {
   // chrome.app.window.create() in the test app.
   AppWindow* CreateTestAppWindow(const std::string& window_create_options);
 
+  // Get the extension icon image for the app window.
+  const gfx::ImageSkia& GetAppIconImage(AppWindow* app_window);
+
  private:
 #if defined(OS_CHROMEOS)
   media_router::MockMediaRouter media_router_;