Adds a common way to initialize logging

mojo/logging/init_logging.cc

Index: mojo/logging/init_logging.cc
diff --git a/mojo/logging/init_logging.cc b/mojo/logging/init_logging.cc
new file mode 100644
index 0000000000000000000000000000000000000000..89e98d6d39d760fbc5a121bb198c6cee008f0788
--- /dev/null
+++ b/mojo/logging/init_logging.cc
@@ -0,0 +1,49 @@
+// Copyright 2015 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 "mojo/logging/init_logging.h"
+
+#include "base/command_line.h"
+#include "base/logging.h"
+
+namespace mojo {
+namespace logging {
+namespace {
+
+::logging::LoggingDestination DetermineLogMode(
+    const base::CommandLine& command_line) {
+  // only use OutputDebugString in debug mode
+#if defined(NDEBUG)
+  bool enable_logging = false;
+  const char* kInvertLoggingSwitch = "enable-logging";
+#else
+  bool enable_logging = true;
+  const char* kInvertLoggingSwitch = "disable-logging";
+#endif
+  const ::logging::LoggingDestination kDefaultLoggingMode =
+      ::logging::LOG_TO_SYSTEM_DEBUG_LOG;
+
+  if (command_line.HasSwitch(kInvertLoggingSwitch))
+    enable_logging = !enable_logging;
+
+  return enable_logging ? kDefaultLoggingMode : ::logging::LOG_NONE;
+}
+
+}  // namespace
+
+void InitLogging() {
+  ::logging::LoggingSettings settings;
+  settings.logging_dest = DetermineLogMode(
+      *base::CommandLine::ForCurrentProcess());
+  ::logging::InitLogging(settings);
+
+  // we want process and thread IDs because we have a lot of things running
+  ::logging::SetLogItems(true,  // enable_process_id
+                         true,  // enable_thread_id
+                         true,  // enable_timestamp
+                         false);  // enable_tickcount
+}
+
+}  // namespace logging
+}  // namespace mojo