Add a BrowserThread::DCheckCurrentlyOn function.

content/public/browser/browser_thread.h

 // Copyright (c) 2012 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.
 
 #ifndef CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_
 #define CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/location.h"
+#include "base/logging.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/task_runner_util.h"
 #include "base/time/time.h"
 #include "content/common/content_export.h"
 
-#if defined(UNIT_TEST)
-#include "base/logging.h"
-#endif  // UNIT_TEST
-
 namespace base {
 class MessageLoop;
 class SequencedWorkerPool;
 class Thread;
 }
 
 namespace content {
 
 class BrowserThreadDelegate;
 class BrowserThreadImpl;
 
+// Use DCHECK_CURRENTLY_ON(BrowserThread::ID) to assert that a function can only
+// be called on the named BrowserThread.
+#define DCHECK_CURRENTLY_ON(thread_identifier)                      \
+  (DCHECK(::content::BrowserThread::CurrentlyOn(thread_identifier)) \
+   << ::content::BrowserThread::GetDCheckCurrentlyOnErrorMessage(   \
+          thread_identifier))
+
 ///////////////////////////////////////////////////////////////////////////////
 // BrowserThread
 //
 // Utility functions for threads that are known by a browser-wide
 // name.  For example, there is one IO thread for the entire browser
 // process, and various pieces of code find it useful to retrieve a
 // pointer to the IO thread's message loop.
 //
 // Invoke a task by thread ID:
 //
@@ skipping 138 matching lines @@
   // Returns the thread pool used for blocking file I/O. Use this object to
   // perform random blocking operations such as file writes or querying the
   // Windows registry.
   static base::SequencedWorkerPool* GetBlockingPool();
 
   // Callable on any thread.  Returns whether the given well-known thread is
   // initialized.
   static bool IsThreadInitialized(ID identifier);
 
   // Callable on any thread.  Returns whether you're currently on a particular
-  // thread.
+  // thread.  To DCHECK this, use the DCHECK_CURRENTLY_ON() macro above.
   static bool CurrentlyOn(ID identifier);
 
   // Callable on any thread.  Returns whether the threads message loop is valid.
   // If this returns false it means the thread is in the process of shutting
   // down.
   static bool IsMessageLoopValid(ID identifier);
 
   // If the current message loop is one of the known threads, returns true and
   // sets identifier to its ID.  Otherwise returns false.
   static bool GetCurrentThreadIdentifier(ID* identifier);
@@ skipping 57 matching lines @@
   //  private:
   //   friend struct BrowserThread::DeleteOnThread<BrowserThread::IO>;
   //   friend class base::DeleteHelper<Foo>;
   //
   //   ~Foo();
   struct DeleteOnUIThread : public DeleteOnThread<UI> { };
   struct DeleteOnIOThread : public DeleteOnThread<IO> { };
   struct DeleteOnFileThread : public DeleteOnThread<FILE> { };
   struct DeleteOnDBThread : public DeleteOnThread<DB> { };
 
+  // Returns an appropriate error message for when DCHECK_CURRENTLY_ON() fails.
+  static std::string GetDCheckCurrentlyOnErrorMessage(ID expected);
+
  private:
   friend class BrowserThreadImpl;
 
   BrowserThread() {}
   DISALLOW_COPY_AND_ASSIGN(BrowserThread);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_H_