Repository: flutter
Issue: Android license status unknown.
Labels: platform-android,tool,d: api docs,t: flutter doctor,a: first hour,customer: crowd,P3,team-android,triaged-android

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## Steps to Reproduce

<!-- Please tell us exactly how to reproduce the problem you are running into. -->

1. `flutter doctor`
*output*
```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, v1.4.9-hotfix.1, on Mac OS X 10.14.4 18E226, locale zh-Hans-CN)
[!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    ✗ Android license status unknown.
      Try re-installing or updating your Android SDK Manager.
      See https://developer.android.com/studio/#downloads or visit
      https://flutter.io/setup/#android-setup for detailed instructions.
[✓] iOS toolchain - develop for iOS devices (Xcode 10.2)
[✓] Android Studio (version 3.3)
[✓] VS Code (version 1.33.1)
[!] Connected device
    ! No devices available

! Doctor found issues in 2 categories.
```
2. `flutter doctor --android-licenses`
*output*
```
A newer version of the Android SDK is required. To update, run:
/Users/eric/Library/Android/sdk/tools/bin/sdkmanager --update
```
3. `sdkmanager --update`
*output*
```
[=======================================] 100% Computing updates...
```
4. `flutter doctor --android-licenses`
*output*
```
A newer version of the Android SDK is required. To update, run:
/Users/eric/Library/Android/sdk/tools/bin/sdkmanager --update
```
## Logs

<!--
      Include the full logs of the commands you are running between the lines
      with the backticks below. If you are running any "flutter" commands,
      please include the output of running them with "--verbose"; for example,
      the output of running "flutter --verbose create foo".
-->

<!-- If possible, paste the output of running `flutter doctor -v` here. -->
*flutter doctor -v*
```
[✓] Flutter (Channel beta, v1.4.9-hotfix.1, on Mac OS X 10.14.4 18E226, locale zh-Hans-CN)
    • Flutter version 1.4.9-hotfix.1 at /Users/eric/dev/flutter
    • Framework revision 88fa7ea403 (4 days ago), 2019-04-11 14:01:46 -0700
    • Engine revision 4737fc5cd8
    • Dart version 2.2.1 (build 2.2.1-dev.4.0 None)

[!] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    • Android SDK at /Users/eric/Library/Android/sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-28, build-tools 28.0.3
    • ANDROID_HOME = /Users/eric/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)
    ✗ Android license status unknown.
      Try re-installing or updating your Android SDK Manager.
      See https://developer.android.com/studio/#downloads or visit
      https://flutter.io/setup/#android-setup for detailed instructions.

[✓] iOS toolchain - develop for iOS devices (Xcode 10.2)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 10.2, Build version 10E125
    • ios-deploy 1.9.4
    • CocoaPods version 1.6.1

[✓] Android Studio (version 3.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 34.0.1
    • Dart plugin version 182.5215
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)

[✓] VS Code (version 1.33.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 2.25.0

[!] Connected device
    ! No devices available

! Doctor found issues in 2 categories.
```
![image](https://user-images.githubusercontent.com/23122353/56191489-03988e80-605f-11e9-8289-e8dad082e4cc.png)