Enable always_declare_return_types lint

And fix a zillion omissions this uncovered.
diff --git a/packages/flutter_tools/bin/flutter_tools.dart b/packages/flutter_tools/bin/flutter_tools.dart
index 482239c..762e6a5 100644
--- a/packages/flutter_tools/bin/flutter_tools.dart
+++ b/packages/flutter_tools/bin/flutter_tools.dart
@@ -4,4 +4,6 @@
 
 import 'package:flutter_tools/executable.dart' as executable;
 
-main(List<String> args) => executable.main(args);
+void main(List<String> args) {
+  executable.main(args);
+}
diff --git a/packages/flutter_tools/lib/src/android/adb.dart b/packages/flutter_tools/lib/src/android/adb.dart
index 0320b3c..e8b648e 100644
--- a/packages/flutter_tools/lib/src/android/adb.dart
+++ b/packages/flutter_tools/lib/src/android/adb.dart
@@ -204,7 +204,7 @@
   /// Device model; can be null. `XT1045`, `Nexus_7`
   String get modelID => _info['model'];
 
-  set modelID(String value) {
+  void set modelID(String value) {
     _info['model'] = value;
   }
 
diff --git a/packages/flutter_tools/lib/src/commands/analyze.dart b/packages/flutter_tools/lib/src/commands/analyze.dart
index 220c639..c6afb1b 100644
--- a/packages/flutter_tools/lib/src/commands/analyze.dart
+++ b/packages/flutter_tools/lib/src/commands/analyze.dart
@@ -288,6 +288,7 @@
     todo: ignore
 linter:
   rules:
+    - always_declare_return_types
     # we'll turn on avoid_as as soon as it doesn't complain about "as dynamic"
     # - avoid_as
     - camel_case_types
diff --git a/packages/flutter_tools/test/adb_test.dart b/packages/flutter_tools/test/adb_test.dart
index f8b505c..168085b 100644
--- a/packages/flutter_tools/test/adb_test.dart
+++ b/packages/flutter_tools/test/adb_test.dart
@@ -5,9 +5,7 @@
 import 'package:flutter_tools/src/android/adb.dart';
 import 'package:test/test.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   Adb adb = new Adb('adb');
 
   // We only test the [Adb] class is we're able to locate the adb binary.
diff --git a/packages/flutter_tools/test/analyze_test.dart b/packages/flutter_tools/test/analyze_test.dart
index 9ff1be2..bddf95f 100644
--- a/packages/flutter_tools/test/analyze_test.dart
+++ b/packages/flutter_tools/test/analyze_test.dart
@@ -14,9 +14,7 @@
 
 import 'src/context.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   AnalysisServer server;
   Directory tempDir;
 
diff --git a/packages/flutter_tools/test/android_device_test.dart b/packages/flutter_tools/test/android_device_test.dart
index 2ad4701..be14072 100644
--- a/packages/flutter_tools/test/android_device_test.dart
+++ b/packages/flutter_tools/test/android_device_test.dart
@@ -7,9 +7,7 @@
 
 import 'src/context.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('android_device', () {
     testUsingContext('stores the requested id', () {
       String deviceId = '1234';
diff --git a/packages/flutter_tools/test/base_utils_test.dart b/packages/flutter_tools/test/base_utils_test.dart
index 053fdd4..ad5a47d 100644
--- a/packages/flutter_tools/test/base_utils_test.dart
+++ b/packages/flutter_tools/test/base_utils_test.dart
@@ -7,9 +7,7 @@
 import 'package:flutter_tools/src/base/utils.dart';
 import 'package:test/test.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('ItemListNotifier', () {
     test('sends notifications', () async {
       ItemListNotifier<String> list = new ItemListNotifier<String>();
diff --git a/packages/flutter_tools/test/context_test.dart b/packages/flutter_tools/test/context_test.dart
index 1de5840..8141909 100644
--- a/packages/flutter_tools/test/context_test.dart
+++ b/packages/flutter_tools/test/context_test.dart
@@ -7,9 +7,7 @@
 import 'package:flutter_tools/src/globals.dart';
 import 'package:test/test.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('DeviceManager', () {
     test('error', () async {
       AppContext context = new AppContext();
diff --git a/packages/flutter_tools/test/create_test.dart b/packages/flutter_tools/test/create_test.dart
index 84e337d..703f8c6 100644
--- a/packages/flutter_tools/test/create_test.dart
+++ b/packages/flutter_tools/test/create_test.dart
@@ -13,9 +13,7 @@
 
 import 'src/context.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('create', () {
     Directory temp;
 
diff --git a/packages/flutter_tools/test/daemon_test.dart b/packages/flutter_tools/test/daemon_test.dart
index 9f986fc..fa34531 100644
--- a/packages/flutter_tools/test/daemon_test.dart
+++ b/packages/flutter_tools/test/daemon_test.dart
@@ -17,9 +17,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   Daemon daemon;
   AppContext appContext;
   NotifyingLogger notifyingLogger;
diff --git a/packages/flutter_tools/test/device_test.dart b/packages/flutter_tools/test/device_test.dart
index 3ea8f09..2bb2fb7 100644
--- a/packages/flutter_tools/test/device_test.dart
+++ b/packages/flutter_tools/test/device_test.dart
@@ -7,9 +7,7 @@
 
 import 'src/context.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('DeviceManager', () {
     testUsingContext('getDevices', () async {
       // Test that DeviceManager.getDevices() doesn't throw.
diff --git a/packages/flutter_tools/test/devices.test.dart b/packages/flutter_tools/test/devices.test.dart
index 767d4ce..49660c7 100644
--- a/packages/flutter_tools/test/devices.test.dart
+++ b/packages/flutter_tools/test/devices.test.dart
@@ -10,9 +10,7 @@
 import 'src/common.dart';
 import 'src/context.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('devices', () {
     testUsingContext('returns 0 when called', () {
       DevicesCommand command = new DevicesCommand();
diff --git a/packages/flutter_tools/test/drive_test.dart b/packages/flutter_tools/test/drive_test.dart
index f95f76c..62c14f6 100644
--- a/packages/flutter_tools/test/drive_test.dart
+++ b/packages/flutter_tools/test/drive_test.dart
@@ -20,9 +20,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('drive', () {
     DriveCommand command;
     Device mockDevice;
@@ -182,7 +180,7 @@
     });
 
     group('findTargetDevice on iOS', () {
-      setOs() {
+      void setOs() {
         when(os.isMacOS).thenReturn(true);
         when(os.isLinux).thenReturn(false);
       }
@@ -222,7 +220,7 @@
     });
 
     group('findTargetDevice on Linux', () {
-      setOs() {
+      void setOs() {
         when(os.isMacOS).thenReturn(false);
         when(os.isLinux).thenReturn(true);
       }
diff --git a/packages/flutter_tools/test/install_test.dart b/packages/flutter_tools/test/install_test.dart
index fc7d2fd..aaa6186 100644
--- a/packages/flutter_tools/test/install_test.dart
+++ b/packages/flutter_tools/test/install_test.dart
@@ -10,9 +10,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('install', () {
     testUsingContext('returns 0 when Android is connected and ready for an install', () {
       InstallCommand command = new InstallCommand();
diff --git a/packages/flutter_tools/test/listen_test.dart b/packages/flutter_tools/test/listen_test.dart
index 701dc24..56bac43 100644
--- a/packages/flutter_tools/test/listen_test.dart
+++ b/packages/flutter_tools/test/listen_test.dart
@@ -9,9 +9,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('listen', () {
     testUsingContext('returns 1 when no device is connected', () {
       ListenCommand command = new ListenCommand(singleRun: true);
diff --git a/packages/flutter_tools/test/logs_test.dart b/packages/flutter_tools/test/logs_test.dart
index ba5bdc9..ef99320 100644
--- a/packages/flutter_tools/test/logs_test.dart
+++ b/packages/flutter_tools/test/logs_test.dart
@@ -9,9 +9,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('logs', () {
     testUsingContext('fail with a bad device id', () {
       LogsCommand command = new LogsCommand();
diff --git a/packages/flutter_tools/test/os_utils_test.dart b/packages/flutter_tools/test/os_utils_test.dart
index 9dacd2f..87a7c28 100644
--- a/packages/flutter_tools/test/os_utils_test.dart
+++ b/packages/flutter_tools/test/os_utils_test.dart
@@ -8,9 +8,7 @@
 import 'package:path/path.dart' as path;
 import 'package:test/test.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('OperatingSystemUtils', () {
     Directory temp;
 
diff --git a/packages/flutter_tools/test/run_test.dart b/packages/flutter_tools/test/run_test.dart
index 8c07516..4f7c7e9 100644
--- a/packages/flutter_tools/test/run_test.dart
+++ b/packages/flutter_tools/test/run_test.dart
@@ -9,9 +9,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('run', () {
     testUsingContext('fails when target not found', () {
       RunCommand command = new RunCommand();
diff --git a/packages/flutter_tools/test/service_protocol_test.dart b/packages/flutter_tools/test/service_protocol_test.dart
index 7c62e57..3498b5c 100644
--- a/packages/flutter_tools/test/service_protocol_test.dart
+++ b/packages/flutter_tools/test/service_protocol_test.dart
@@ -9,9 +9,7 @@
 
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('service_protocol', () {
     test('Discovery Heartbeat', () async {
       MockDeviceLogReader logReader = new MockDeviceLogReader();
diff --git a/packages/flutter_tools/test/stop_test.dart b/packages/flutter_tools/test/stop_test.dart
index 112a9fc..d3c5f31 100644
--- a/packages/flutter_tools/test/stop_test.dart
+++ b/packages/flutter_tools/test/stop_test.dart
@@ -12,9 +12,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('stop', () {
     testUsingContext('returns 0 when Android is connected and ready to be stopped', () {
       StopCommand command = new StopCommand();
diff --git a/packages/flutter_tools/test/trace_test.dart b/packages/flutter_tools/test/trace_test.dart
index 5fc2cd7..e987067 100644
--- a/packages/flutter_tools/test/trace_test.dart
+++ b/packages/flutter_tools/test/trace_test.dart
@@ -9,9 +9,7 @@
 import 'src/context.dart';
 import 'src/mocks.dart';
 
-main() => defineTests();
-
-defineTests() {
+void main() {
   group('trace', () {
     testUsingContext('returns 1 when no Android device is connected', () {
       TraceCommand command = new TraceCommand();