Mojo Log service and a thread-safe client library.

mojo/services/log/interfaces/entry.mojom

+// 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.
+
+module mojo.log;
+
+// Log levels: Levels less than |kLogLevelVerbose| are valid and indicate
+// greater levels of verbosity. Levels greater than |kLogLevelFatal| should be
+// taken to be equivalent to |kLogLevelFatal|.
+const int32 kLogLevelVerbose = -1;
+const int32 kLogLevelInfo = 0;
+const int32 kLogLevelWarning = 1;
+const int32 kLogLevelError = 2;
+const int32 kLogLevelFatal = 3;
+
+// Describes a log message and its origin in source code. It is used by the
+// |mojo::log::Log| service (see log.mojom).
+struct Entry {
+  // Client-side timestamp, in microseconds.
+  int64 timestamp;
+  // The log level for this message. See the log level constants described
+  // above.
+  int32 log_level;
+
+  string? message;
+
+  // The client source file this log entry originated from.  It is optional.   
+  string? source_file;
+  // |source_line| refers to the line in |source_file| the log entry came from. 
+  // |source_line| is ignored if:
+  //   - |source_file| is null.
+  //   - its value is 0 (which is an invalid value).
+  uint32 source_line = 0;
+};