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.
+#define SYNCFS_LOG(severity, format, ...) \
+    sync_file_system::util::Log( \
+        FROM_HERE, logging::LOG_##severity, format, ##__VA_ARGS__);

[tzik, 2013/05/24 11:17:38]

This is a shorthand of
util::Log(FROM_HERE, logging::LOG_WARNING,
          "abc%s", "ba");
with
SYNCFS_LOG(WARNING, "abc%s", "ba")

But, this seem not worth defining new macro in .h as our coding style warns:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Prepro...

Yes, once I suggested you to use macro to insert FROM_HERE, though let me change
my recommendation:
Could we directly write down FROM_HERE and logging::LOG_ for each call site?

[calvinlo, 2013/05/25 06:03:25]

Ah yes, after reading the Style guide reference you linked I agree that using
this Macro is a great idea here. I will change all the call sites to be regular
function calls.

 
 // 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_