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

chrome/browser/sync_file_system/logger.cc

Index: chrome/browser/sync_file_system/logger.cc
diff --git a/chrome/browser/sync_file_system/logger.cc b/chrome/browser/sync_file_system/logger.cc
index 55705c95b16666dccbe2c553a4e7d027887471a5..64c89bbe0cf51aa4be025f77307ed66de869791c 100644
--- a/chrome/browser/sync_file_system/logger.cc
+++ b/chrome/browser/sync_file_system/logger.cc
@@ -17,7 +17,48 @@ static base::LazyInstance<google_apis::EventLogger> g_logger =
 
 }  // namespace
 
-void Log(const char* format, ...) {
+std::string LogSeverityToString(logging::LogSeverity level) {
+  switch (level) {
+    case logging::LOG_ERROR:
+      return "Error";
+    case logging::LOG_WARNING:
+      return "Warning";
+    case logging::LOG_INFO:
+      return "Info";
+  }
+
+  NOTREACHED();
+  return "Unknown Log Severity";
+}
+
+// Need helper function since the LOG macro can't handle argument values.
+void LogToConsole(logging::LogSeverity level, std::string log_event) {
+  switch (level) {
+    case logging::LOG_ERROR:
+      LOG(ERROR) << log_event;
+      return;
+    case logging::LOG_WARNING:
+      LOG(WARNING) << log_event;
+      return;
+    case logging::LOG_INFO:
+      LOG(INFO) << log_event;
+      return;
+  }
+
+  LOG(FATAL) << "LogToConsole() missing case for LogSeverity=" << level;
+  NOTREACHED();
+}
+
+void Log(logging::LogSeverity level, std::string& format, ...) {
+  va_list args;
+  Log(level, format.c_str(), args);
+}
+
+void Log(logging::LogSeverity level, const char* format, ...) {
+  // Ignore log if level is not high enough.
+  if (level < logging::GetMinLogLevel())
+    return;
+
   std::string what;
 
   va_list args;
@@ -28,7 +69,11 @@ void Log(const char* format, ...) {
   // On thread-safety: LazyInstance guarantees thread-safety for the object
   // creation. EventLogger::Log() internally maintains the lock.
   google_apis::EventLogger* ptr = g_logger.Pointer();
-  ptr->Log("%s", what.c_str());
+  std::string level_string = "[" + LogSeverityToString(level) + "] ";
+  ptr->Log("%s", (level_string + what).c_str());
+
+  // Mirror log to console just in case syncfs-internals page crashes.
+  LogToConsole(level, what);
 }
 
 std::vector<google_apis::EventLogger::Event> GetLogHistory() {