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

chrome/browser/sync_file_system/logger.cc

 // 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.
 
 #include "chrome/browser/sync_file_system/logger.h"
 
 #include "base/lazy_instance.h"
 #include "base/stringprintf.h"
 #include "chrome/browser/google_apis/event_logger.h"
 
 namespace sync_file_system {
 namespace util {
 namespace {
 
 static base::LazyInstance<google_apis::EventLogger> g_logger =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // 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;
   va_start(args, format);
   base::StringAppendV(&what, format, args);
   va_end(args);
 
   // 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() {
   google_apis::EventLogger* ptr = g_logger.Pointer();
   return ptr->GetHistory();
 }
 
 }  // namespace util
 }  // namespace sync_file_system