Add 'flog' service implementation.

mojo/services/flog/interfaces/flog.mojom

 // Copyright 2016 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.
 
 [DartPackage="mojo_services"]
 module mojo.flog;
 
-// TODO(dalesat): Move out of media to somewhere more generic.
-
 // Exposed by the log service to enable creation and consumption of logs.
 [ServiceName="mojo::flog::FlogService"]
 interface FlogService {
   // Creates a new logger.
   CreateLogger(FlogLogger& logger, string label);
 
   // Gets the descriptions of all logs.
   GetLogDescriptions() => (array<FlogDescription> descriptions);
 
   // Gets a reader for the specified log.
   CreateReader(FlogReader& reader, uint32 log_id);
 };
 
 // A logger that logs messages regarding multiple channels.
 interface FlogLogger {
   // Logs the creation of a channel.
   LogChannelCreation(int64 time_us, uint32 channel_id, string type_name);
 
   // Logs a message sent to an existing channel.
   LogChannelMessage(int64 time_us, uint32 channel_id, array<uint8> data);
 
   // Logs the deletion of a channel.
   LogChannelDeletion(int64 time_us, uint32 channel_id);
+
+  // TODO(dalesat): Add a method for logging text/file/line
 };
 
 // A reader that reads messages from one or more logs.
 interface FlogReader {
   // Gets entries from the log starting and the specified index (entries are
   // indexed starting at 0). If the log is open, the callback will be called
   // when max_count entries are avaiable starting at start_index. If the log
   // is closed, the callback will be called immediately with as many entries
   // as are available starting at start_index and not exceeding max_count
-  // entries. entry_count and open refer to the entire log at the time the
-  // callback occurred.
+  // entries.
   GetEntries(uint32 start_index, uint32 max_count) =>
-      (array<FlogEntry> entries, uint32 entry_count, bool open);
+      (array<FlogEntry> entries);
 };
 
+// Describes a log.
 struct FlogDescription {
+  uint32 log_id;
   string label;
-  uint32 log_id;
-  uint32 entry_count;
-  int64 start_time_us;
-  int64 stop_time_us;
   bool open;
 };
 
+// Log entry produced by |FlogReader|. Entry type is determined by interrogating
+// the |details| field.
 struct FlogEntry {
   int64 time_us;
   uint32 log_id;
   uint32 channel_id;
   FlogEntryDetails? details;
 };
 
 union FlogEntryDetails {
   FlogChannelCreationEntryDetails channel_creation;
   FlogChannelMessageEntryDetails channel_message;
+  FlogChannelDeletionEntryDetails channel_deletion;
+  // TODO(dalesat): Add details for text/file/line entry
 };
 
 struct FlogChannelCreationEntryDetails {
   string type_name;
 };
 
 struct FlogChannelMessageEntryDetails {
   array<uint8> data;
 };
+
+struct FlogChannelDeletionEntryDetails {
+};