Add logs command and android implementation.

packages/flutter_tools/bin/sky_tools.dart

@@ -13,6 +13,7 @@ import 'package:sky_tools/src/build.dart';
 import 'package:sky_tools/src/cache.dart';
 import 'package:sky_tools/src/init.dart';
 import 'package:sky_tools/src/install.dart';
+import 'package:sky_tools/src/logs.dart';
 import 'package:sky_tools/src/run_mojo.dart';
 import 'package:sky_tools/src/start.dart';
 import 'package:sky_tools/src/stop.dart';
@@ -148,6 +149,7 @@ void main(List<String> args) {
     ..addCommand(new CacheCommand())
     ..addCommand(new InitCommand())
     ..addCommand(new InstallCommand())
+    ..addCommand(new LogsCommand())
     ..addCommand(new RunMojoCommand())
     ..addCommand(new StartCommand())
     ..addCommand(new StopCommand())

packages/flutter_tools/lib/src/device.dart

@@ -317,6 +317,26 @@ class AndroidDevice extends _Device {
     return true;
   }
 
+  void clearLogs() {
+    runSync([adbPath, 'logcat', '-c']);
+  }
+
+  Future<int> logs({bool clear: false}) {
+    if (clear) {
+      clearLogs();
+    }
+
+    return runCommandAndStreamOutput([
+      adbPath,
+      'logcat',
+      '-v',
+      'tag', // Only log the tag and the message
+      '-s',
+      'sky',
+      'chromium',
+    ]);
+  }
+
   @override
   bool isConnected() => _hasValidAndroid;
 }

packages/flutter_tools/lib/src/logs.dart

@@ -0,0 +1,42 @@
+// 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.
+
+library sky_tools.logs;
+
+import 'dart:async';
+
+import 'package:args/command_runner.dart';
+import 'package:logging/logging.dart';
+import 'package:sky_tools/src/device.dart';
+
+final Logger _logging = new Logger('sky_tools.logs');
+
+class LogsCommand extends Command {
+  final name = 'logs';
+  final description = 'Show logs for running Sky apps.';
+  AndroidDevice android = null;
+
+  LogsCommand([this.android]) {
+    argParser.addFlag('clear',
+        negatable: false,
+        help: 'Clear log history before reading from logs (Android only).');
+    if (android == null) {
+      android = new AndroidDevice();
+    }
+  }
+
+  @override
+  Future<int> run() async {
+    Future<int> androidLogProcess = null;
+    if (android.isConnected()) {
+      androidLogProcess = android.logs(clear: argResults['clear']);
+    }
+
+    if (androidLogProcess != null) {
+      await androidLogProcess;
+    }
+
+    return 0;
+  }
+}