Improve usage documentation of scoped task environments.

content/public/test/test_browser_thread_bundle.h

Index: content/public/test/test_browser_thread_bundle.h
diff --git a/content/public/test/test_browser_thread_bundle.h b/content/public/test/test_browser_thread_bundle.h
index 15cdba8f5c6b350876bfb172fe04a15de5dac492..0f1b455947cd683728a00f88a6bc54d576d34484 100644
--- a/content/public/test/test_browser_thread_bundle.h
+++ b/content/public/test/test_browser_thread_bundle.h
@@ -53,6 +53,24 @@
 //
 // DONT_CREATE_THREADS should only be used when the options specify at least
 // one real thread other than the main thread.
+//
+// Basic usage:
+//
+//   class MyTestFixture : public testing::Test {
+//    public:
+//     (...)
+//
+//    protected:
+//     // Must be first member (or at least before any member that cares about
+//     // tasks) to be initialized first and destroyed last. protected instead
+//     // of private visibility will allow controlling the task environment
+//     // (e.g. clock) once such features are added (see
+//     // base::test::ScopedTaskEnvironment for details), until then it at least
+//     // doesn't hurt :).
+//     content::TestBrowserThreadBundle test_browser_thread_bundle_;
+//
+//     // Other members go here (or further below in private section.)
+//   };
 
 #ifndef CONTENT_PUBLIC_TEST_TEST_BROWSER_THREAD_BUNDLE_H_
 #define CONTENT_PUBLIC_TEST_TEST_BROWSER_THREAD_BUNDLE_H_