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..741c4b95250c58771ffd377950647d9cde8437c8 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 {
@@ -15,9 +16,13 @@ namespace sync_file_system {
 // 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(logging::LogSeverity level, const char* format, ...)
+    PRINTF_FORMAT(2, 3);
 
 // Returns the log history.
 // This function can be called from any thread.