Dart: Remove unused library and example

mojo/common/dart/lib/src/trace_provider_impl.dart

-// 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.
-
-import 'dart:async';
-
-import 'package:mojo/core.dart';
-import 'package:mojo_services/tracing/tracing.mojom.dart';
-
-enum TraceSendTiming {
-  IMMEDIATE,
-  // TODO: Add BATCHED?
-  AT_END,
-}
-
-class TraceProviderImpl implements TraceProvider {
-  // Any messages sent before the tracing service connects to us will be
-  // recorded and kept until one second after construction of the trace
-  // provider. If the tracing service connects before that time, we will replay
-  // the recorded trace events.
-  //
-  // This allows the client to record trace events early during initialization
-  // of the app.
-  List<String> _message_queue;
-  bool _enqueuing;
-
-  TraceProviderStub _stub;
-  TraceRecorderProxy _recorder;
-  // TODO(rudominer) We currently ignore _categories.
-  String _categories;
-
-  TraceSendTiming _timing;
-
-  TraceProviderImpl([TraceSendTiming timing = TraceSendTiming.IMMEDIATE]) {
-    _message_queue = [];
-    _enqueuing = true;
-    _timing = timing;
-    new Future.delayed(const Duration(seconds: 1), () {
-      if (_enqueuing) {
-        _enqueuing = false;
-        _message_queue.clear();
-      }
-    });
-  }
-
-  void connect(MojoMessagePipeEndpoint e) {
-    _stub = TraceProviderStub.newFromEndpoint(e);
-    _stub.impl = this;
-  }
-
-  @override
-  void startTracing(String categories, TraceRecorderProxy recorder) {
-    assert(_recorder == null);
-    _recorder = recorder;
-    _categories = categories;
-    _enqueuing = false;
-    if (_timing == TraceSendTiming.IMMEDIATE) {
-      for (String message in _message_queue) {
-        _recorder.ptr.record(message);
-      }
-      _message_queue.clear();
-    }
-  }
-
-  @override
-  void stopTracing() {
-    assert(_recorder != null);
-    if (_timing == TraceSendTiming.AT_END) {
-      for (String message in _message_queue) {
-        _recorder.ptr.record(message);
-      }
-      _message_queue.clear();
-    }
-    _recorder.close();
-    _recorder = null;
-  }
-
-  bool isActive() {
-    return _enqueuing || _recorder != null;
-  }
-
-  void sendTraceMessage(String message) {
-    switch (_timing) {
-      case TraceSendTiming.IMMEDIATE:
-        if (_recorder != null) {
-          _recorder.ptr.record(message);
-        } else if (_enqueuing) {
-          _message_queue.add(message);
-        }
-        break;
-      case TraceSendTiming.AT_END:
-        if (isActive()) {
-          _message_queue.add(message);
-        }
-        break;
-    }
-  }
-}