Mirror syncfs log to console and WebUI, with LogSeverity support.

chrome/browser/sync_file_system/logger.h

 // Copyright 2013 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 CHROME_BROWSER_SYNC_FILE_SYSTEM_LOGGER_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_LOGGER_H_
 
 #include <string>
 #include <vector>
 
+#include "base/location.h"
+#include "base/logging.h"
 #include "chrome/browser/google_apis/event_logger.h"
 
 namespace sync_file_system {
 // Originally wanted to use 'logging' here, but it conflicts with
 // base/logging.h, and breaks DCHECK() and friends.
 namespace util {
 
+// Resets the log.
+void ClearLog();
+
 // Logs a message using printf format.
 // This function can be called from any thread.
-void Log(const char* format, ...) PRINTF_FORMAT(1, 2);
+void Log(tracked_objects::Location location,
+         logging::LogSeverity level,
+         const char* format,
+         ...)
+    PRINTF_FORMAT(3, 4);
+
+// Macros to keep the file and line location of the original Log calls.
+// Unfortunately the second version with no args seems to be needed to keep the
+// compiler happy.
+#define SYNCFS_LOG_WITH_ARGS(severity, format, ...) \
+    sync_file_system::util::Log( \
+        FROM_HERE, logging::LOG_##severity, format, __VA_ARGS__);
+#define SYNCFS_LOG_WITH_NO_ARGS(severity, message) \
+    sync_file_system::util::Log(FROM_HERE, logging::LOG_##severity, message);
+#define GET_SYNCFS_LOG(_1,_2,_3,NAME,...) NAME
+#define SYNCFS_LOG(...) \
+    GET_SYNCFS_LOG(__VA_ARGS__, SYNCFS_LOG_WITH_ARGS, SYNCFS_LOG_WITH_NO_ARGS) \
+        (__VA_ARGS__)

[tzik, 2013/05/24 04:08:32]

Could you avoid using macros in other than simplest case?
This looks too complicated for me to accept...

If this is needed, we should use Log directly.

[calvinlo, 2013/05/24 05:12:43]

Ok, I did a little bit more research on MARCROs and I think I figured out the
magic syntax to make this work with just a single macro now.

 
 // Returns the log history.
 // This function can be called from any thread.
 std::vector<google_apis::EventLogger::Event> GetLogHistory();
 
 }  // namespace util
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_LOGGER_H_