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

chrome/browser/sync_file_system/logger.h

Index: chrome/browser/sync_file_system/logger.h
diff --git a/chrome/browser/sync_file_system/logger.h b/chrome/browser/sync_file_system/logger.h
index 20a223c614a78e633a68dd0224e5fba3ec830b03..ac522ea5af5eb03a3f21e62148d4f6e2a2693ebe 100644
--- a/chrome/browser/sync_file_system/logger.h
+++ b/chrome/browser/sync_file_system/logger.h
@@ -8,6 +8,7 @@
 #include <string>
 #include <vector>
 
+#include "base/logging.h"
 #include "chrome/browser/google_apis/event_logger.h"
 
 namespace sync_file_system {
@@ -17,7 +18,11 @@ namespace util {
 
 // 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(logging::LogSeverity level, const char* format, ...)
+    PRINTF_FORMAT(2, 3);
+
+// Convinience function so c_str() doesn't always have to be called on strings.
+void Log(logging::LogSeverity level, std::string& format, ...);
 
 // Returns the log history.
 // This function can be called from any thread.