Add size benchmark for hello_world (#18522)

dev/devicelab/bin/tasks/hello_world_android__compile.dart

+// Copyright 2018 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:flutter_devicelab/framework/adb.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/tasks/perf_tests.dart';
+
+Future<Null> main() async {
+  deviceOperatingSystem = DeviceOperatingSystem.android;
+  await task(createHelloWorldCompileTest());
+}

dev/devicelab/bin/tasks/hello_world_ios__compile.dart

+// Copyright 2018 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:flutter_devicelab/framework/adb.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/tasks/perf_tests.dart';
+
+Future<Null> main() async {
+  deviceOperatingSystem = DeviceOperatingSystem.ios;
+  await task(createHelloWorldCompileTest());
+}

dev/devicelab/lib/tasks/perf_tests.dart

@@ -43,6 +43,10 @@ TaskFunction createFlutterGalleryCompileTest() {
   return new CompileTest('${flutterDirectory.path}/examples/flutter_gallery').run;
 }
 
+TaskFunction createHelloWorldCompileTest() {
+  return new CompileTest('${flutterDirectory.path}/examples/hello_world').run;
+}
+
 TaskFunction createComplexLayoutCompileTest() {
   return new CompileTest('${flutterDirectory.path}/dev/benchmarks/complex_layout').run;
 }

dev/devicelab/manifest.yaml

@@ -182,6 +182,12 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["mac/android"]
 
+  hello_world_android__compile:
+    description: >
+      Measures the APK size of Hello World.
+    stage: devicelab
+    required_agent_capabilities: ["mac/android"]
+
   hello_world__memory:
     description: >
       Measures starting memory usage of the simplest Flutter app.
@@ -333,6 +339,12 @@ tasks:
     stage: devicelab_ios
     required_agent_capabilities: ["mac/ios"]
 
+  hello_world_ios__compile:
+    description: >
+      Measures the IPA size of Hello World.
+    stage: devicelab
+    required_agent_capabilities: ["mac/ios"]
+
   microbenchmarks_ios:
     description: >
       Runs benchmarks from dev/benchmarks/microbenchmarks on iOS.