Repository: flutter
Issue: Splash Screen configurations reset during Flutter Initialization
Labels: platform-android,engine,a: fidelity,e: embedder,c: proposal,P2,team-android,triaged-android

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## Steps to Reproduce

<!-- You must include full steps to reproduce so that we can reproduce the problem. -->

1. Open any existing flutter project.
2. Edit the file `android\app\src\main\res\values\styles.xml` as follows:

```
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <style name="LaunchTheme" parent="@android:style/Theme.Light.NoTitleBar">
        <item name="android:windowBackground">@drawable/launch_background</item>
        <item name="android:windowFullscreen">true</item>

    </style>

    <style name="NormalTheme" parent="@android:style/Theme.Light.NoTitleBar">
        <item name="android:windowBackground">@android:color/white</item>

    </style>
</resources>
```

**Expected results:** <!-- what did you want to see? -->

I would expect splash screen to be shown while the app is in fullscreen.

**Actual results:** <!-- what did you see? -->

According to the Flutter documentation [here](https://flutter.dev/docs/development/ui/advanced/splash-screen), 

> In Android, there are two separate screens that you can control: a launch screen shown while your Android app initializes, and a splash screen that displays while the Flutter experience initializes.

Technically, the configuration above is for the launch screen, what happens is when the app runs, the configurations work and the app starts in full screen like intended for the launch screen, but when time for "initializing the flutter experience" starts and the splash screen is to be shown, everything is reset. By everything I mean any configurations be it, hiding status bar, setting status bar color etc... They are all reset and this even comes with a jump smilar to one described in this issue #47634 . 

According to this 

> To display a splash screen with the same visual as a launch screen, reference the same @drawable/launch_background in the io.flutter.embedding.android.SplashScreenDrawable meta-data.

 And I aready do this in AndroidManifest.xml 

```
<meta-data
    android:name="io.flutter.embedding.android.SplashScreenDrawable"
    android:resource="@drawable/launch_background"
    />
```

If only I could be able to customize the SplashScreen like I could with the `LaunchTheme` like demonstrated at the beginning. I think it would be great otherwise customizing the launch screen without customizing the splash screen would make it like it has reset 

<details>
  <summary>Logs</summary>

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
[√] Flutter (Channel stable, 1.20.3, on Microsoft Windows [Version 10.0.19041.450], locale en-UG)
    • Flutter version 1.20.3 at C:\flutter
    • Framework revision 216dee60c0 (7 days ago), 2020-09-01 12:24:47 -0700
    • Engine revision d1bc06f032
    • Dart version 2.9.2


[√] Android toolchain - develop for Android devices (Android SDK version 29.0.1)
    • Android SDK at C:\Android\sdk
    • Platform android-29, build-tools 29.0.1
    • ANDROID_HOME = C:\Android\sdk
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)
    • All Android licenses accepted.

[√] Android Studio (version 3.4)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 39.0.1
    • Dart plugin version 183.6270
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)

[√] VS Code (version 1.48.2)
    • VS Code at C:\Users\Reagan Realones\AppData\Local\Programs\Microsoft VS Code
    • Flutter extension version 3.12.2

[√] Connected device (1 available)
    • TECNO AB7 (mobile) • 0456725988000504 • android-arm64 • Android 9 (API 28)

• No issues found!
```

</details>