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| are
+// invalid and 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;
+
+// TODO(vardhan):  Should we split this into ClientEntry and ServiceEntry? 
+// EntryMetadata is only meant to be used by a log service. 
+struct Entry {
+  // Client-supplied information:
+  // Client-side timestamp.
+  int64 timestamp;
+  // Log level: one of |kLogLevel...|.
+  int32 log_level;
+
+  // The client source location this log originated from.
+  string? source_file;
+  uint32 source_line = 0;
+  
+  // Message.
+  string? message;
+
+  // Service-supplied information, not set by the client.
+  EntryMetadata? metadata;
+};
+
+struct EntryMetadata {
+  int64 server_timestamp;
+  string source;
+};