Issue 1:
import 'dart:async';

import 'package:flutter/widgets.dart';

final GlobalKey _kKey = new GlobalKey();
Future main() async {
runApp(new Block(
children: new List<Widget>.generate(
3,
(_) => new Padding(
padding: const EdgeInsets.all(8.0),
child: new Container(
key: _kKey,
width: 100.0,
height: 100.0,
decoration: new BoxDecoration(
backgroundColor: new Color(0xFFFFFF00)))))));
}

Assert:

10:35:01.044: I/flutter : ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
10:35:01.055: I/flutter : The following assertion was thrown building RawGestureDetector([GlobalKey 273613476]; state:
10:35:01.058: I/flutter : RawGestureDetectorState(304216675; gestures: vertical drag; behavior: opaque)):
10:35:01.062: I/flutter : scheduleBuildFor() called for a widget for which a build was already scheduled.
10:35:01.065: I/flutter : The method was called for the following element:
10:35:01.068: I/flutter : DecoratedBox(dirty; renderObject: RenderDecoratedBox NEEDS-LAYOUT DETACHED)
10:35:01.072: I/flutter : The current dirty list consists of:
10:35:01.075: I/flutter : [DecoratedBox(dirty; renderObject: RenderDecoratedBox NEEDS-LAYOUT DETACHED)]
10:35:01.078: I/flutter : This usually indicates that a widget was rebuilt outside the build phase (thus marking the element
10:35:01.082: I/flutter : as clean even though it is still in the dirty list). This should not be possible and is probably
10:35:01.085: I/flutter : caused by a bug in the widgets framework. Please report it:
10:35:01.087: I/flutter : https://github.com/flutter/flutter/issues/new
10:35:01.090: I/flutter : To debug this issue, consider setting the debugPrintScheduleBuildForStacks and
10:35:01.093: I/flutter : debugPrintBuildDirtyElements flags to true and looking for a call to scheduleBuildFor for a widget
10:35:01.096: I/flutter : that is labeled "ALREADY IN LIST".
10:35:01.243: I/flutter :
10:35:01.247: I/flutter : When the exception was thrown, this was the stack:
10:35:01.272: I/flutter : #0 BuildOwner.scheduleBuildFor.<anonymous closure> (package:flutter/src/widgets/framework.dart:1531:9)
10:35:01.275: I/flutter : #2 BuildOwner.scheduleBuildFor (package:flutter/src/widgets/framework.dart:1527:12)
10:35:01.278: I/flutter : #3 BuildableElement.markNeedsBuild (package:flutter/src/widgets/framework.dart:2538:11)
10:35:01.282: I/flutter : #4 BuildableElement.dependenciesChanged (package:flutter/src/widgets/framework.dart:2584:5)
10:35:01.285: I/flutter : #5 BuildableElement.activate (package:flutter/src/widgets/framework.dart:2599:7)
10:35:01.289: I/flutter : #6 Element._activateRecursively (package:flutter/src/widgets/framework.dart:2194:13)
10:35:01.292: I/flutter : #7 SingleChildRenderObjectElement.visitChildren (package:flutter/src/widgets/framework.dart:3424:14)
10:35:01.295: I/flutter : #8 Element._activateRecursively (package:flutter/src/widgets/framework.dart:2196:13)
10:35:01.298: I/flutter : #9 ComponentElement.visitChildren (package:flutter/src/widgets/framework.dart:2690:14)
10:35:01.301: I/flutter : #10 Element._activateRecursively (package:flutter/src/widgets/framework.dart:2196:13)
10:35:01.305: I/flutter : #11 Element._activateWithParent (package:flutter/src/widgets/framework.dart:2187:5)
10:35:01.307: I/flutter : #12 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2131:18)
10:35:01.310: I/flutter : #13 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.313: I/flutter : #14 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
10:35:01.316: I/flutter : #15 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.319: I/flutter : #16 MultiChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3532:32)
10:35:01.322: I/flutter : #17 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.325: I/flutter : #18 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.327: I/flutter : #19 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
10:35:01.330: I/flutter : #20 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.333: I/flutter : #21 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.336: I/flutter : #22 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
10:35:01.339: I/flutter : #23 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.342: I/flutter : #24 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.346: I/flutter : #25 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
10:35:01.349: I/flutter : #26 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.352: I/flutter : #27 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.355: I/flutter : #28 SingleChildRenderObjectElement.mount (package:flutter/src/widgets/framework.dart:3436:14)
10:35:01.358: I/flutter : #29 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.361: I/flutter : #30 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.364: I/flutter : #31 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:2678:16)
10:35:01.367: I/flutter : #32 BuildableElement.rebuild (package:flutter/src/widgets/framework.dart:2567:5)
10:35:01.370: I/flutter : #33 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:2652:5)
10:35:01.373: I/flutter : #34 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:2768:22)
10:35:01.376: I/flutter : #35 ComponentElement.mount (package:flutter/src/widgets/framework.dart:2647:5)
10:35:01.379: I/flutter : #36 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.383: I/flutter : #37 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.386: I/flutter : #38 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:2678:16)
10:35:01.389: I/flutter : #39 BuildableElement.rebuild (package:flutter/src/widgets/framework.dart:2567:5)
10:35:01.392: I/flutter : #40 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:2652:5)
10:35:01.395: I/flutter : #41 StatefulElement._firstBuild (package:flutter/src/widgets/framework.dart:2768:22)
10:35:01.399: I/flutter : #42 ComponentElement.mount (package:flutter/src/widgets/framework.dart:2647:5)
10:35:01.402: I/flutter : #43 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.405: I/flutter : #44 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.409: I/flutter : #45 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:2678:16)
10:35:01.412: I/flutter : #46 BuildableElement.rebuild (package:flutter/src/widgets/framework.dart:2567:5)
10:35:01.415: I/flutter : #47 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:2652:5)
10:35:01.418: I/flutter : #48 ComponentElement.mount (package:flutter/src/widgets/framework.dart:2647:5)
10:35:01.421: I/flutter : #49 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.424: I/flutter : #50 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.428: I/flutter : #51 ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:2678:16)
10:35:01.431: I/flutter : #52 BuildableElement.rebuild (package:flutter/src/widgets/framework.dart:2567:5)
10:35:01.434: I/flutter : #53 ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:2652:5)
10:35:01.437: I/flutter : #54 ComponentElement.mount (package:flutter/src/widgets/framework.dart:2647:5)
10:35:01.440: I/flutter : #55 Element.inflateWidget (package:flutter/src/widgets/framework.dart:2139:14)
10:35:01.444: I/flutter : #56 Element.updateChild (package:flutter/src/widgets/framework.dart:1970:12)
10:35:01.447: I/flutter : #57 RenderObjectToWidgetElement._rebuild (package:flutter/src/widgets/binding.dart:518:16)
10:35:01.449: I/flutter : #58 RenderObjectToWidgetElement.mount (package:flutter/src/widgets/binding.dart:489:5)
10:35:01.453: I/flutter : #59 RenderObjectToWidgetAdapter.attachToRenderTree.<anonymous closure> (package:flutter/src/widgets/binding.dart:435:17)
10:35:01.456: I/flutter : #60 BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:1649:19)
10:35:01.459: I/flutter : #61 RenderObjectToWidgetAdapter.attachToRenderTree (package:flutter/src/widgets/binding.dart:434:13)
10:35:01.462: I/flutter : #62 BindingBase&SchedulerBinding&GestureBinding&ServicesBinding&RendererBinding&WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:336:7)
10:35:01.465: I/flutter : #63 runApp (package:flutter/src/widgets/binding.dart:367:7)
10:35:01.468: I/flutter : #64 main.<main_async_body> (/data/user/0/com.google.fuchsia.armadillo/cache/armadillowvraes/lib/main.dart:11:3)
10:35:01.471: I/flutter : (elided 4 frames from class _AssertionError and package dart:async)
10:35:01.475: I/flutter : ════════════════════════════════════════════════════════════════════════════════════════════════════

Issue 2:
What went wrong:

Execution failed for task ':app:preDebugBuild'.

Android dependency 'com.google.android.gms:play-services-tasks' has different version for the compile (11.8.0) and runtime (15.0.1) classpath. You should manually set the same version via DependencyResolution

Microsoft Windows [Version 10.0.17134.165]
(c) 2018 Microsoft Corporation. All rights reserved.

C:\FlutterProjects\wait_not>flutter doctor -v
[√] Flutter (Channel dev, v0.5.8, on Microsoft Windows [Version 10.0.17134.165], locale en-US)
• Flutter version 0.5.8 at C:\git\flutter
• Framework revision e4b989bf3d (3 days ago), 2018-08-09 09:45:44 -0700
• Engine revision 3777931801
• Dart version 2.0.0-dev.69.5.flutter-eab492385c

[√] Android toolchain - develop for Android devices (Android SDK 27.0.3)
• Android SDK at C:\Users\admin\AppData\Local\Android\sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-27, build-tools 27.0.3
• Java binary at: C:\Program Files\Android\Android Studio1\jre\bin\java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b02)
• All Android licenses accepted.

[√] Android Studio (version 3.1)
• Android Studio at C:\Program Files\Android\Android Studio1
• Flutter plugin version 27.1.1
• Dart plugin version 173.4700
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1024-b02)

[√] IntelliJ IDEA Community Edition (version 2017.2)
• IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2017.2.5
• Flutter plugin version 19.1
• Dart plugin version 172.4343.25

[√] VS Code, 64-bit edition (version 1.25.1)
• VS Code at C:\Program Files\Microsoft VS Code
• Flutter extension version 2.17.1

[√] Connected devices (1 available)
• SCH I959 • 4d004c0e6d66401f • android-arm • Android 5.0.1 (API 21)

• No issues found!