Repository: flutter
Issue: Animation in sliver renders background in wrong position
Labels: framework,a: animation,f: material design,f: scrolling,d: api docs,has reproducible steps,P2,found in release: 3.0,found in release: 3.1,team-design,triaged-design

## Steps to Reproduce

When using a `CustomScrollView` with a `AnimatedSize` widget (inside a `SliverToBoxAdapter` -> Column) which resizes based on a simple toggle and below a `Ink` with a background color, the background color is rendered in the wrong place while the `child` of the `Ink` is in the correct place at all times.

I have made a simple app which shows the problem: https://github.com/hpoul/sliver_animation_background/blob/master/lib/main.dart#L77-L91

![flutter_sliver_animation_background](https://user-images.githubusercontent.com/313066/60837258-06230400-a1c8-11e9-94ce-a5bb5b685f6c.gif)

(once i manually scroll the background renders correctly, it's only happening when the animation is triggered through the `AnimatedSize` widget. The problem only happens with the `CustomScrollView`, putting the `Column` directly into the `body` of the `Scaffold` works as intended.)

(tested on iPhone Xr 12.2 simulator, Android Simulator 8.1 and physical Android Pie device)

## Logs

```
Herbys-MacBook-Pro-2017:sliver_animation_background$ flutter doctor -v
[✓] Flutter (Channel master, v1.8.1-pre.23, on Mac OS X 10.14.5 18F132, locale en-AT)
    • Flutter version 1.8.1-pre.23 at /Users/herbert/dev/flutter/flutter
    • Framework revision 3bf91b5436 (3 days ago), 2019-07-05 12:59:32 -0700
    • Engine revision 3c51a7bfff
    • Dart version 2.5.0 (build 2.5.0-dev.0.0 b5aeaa6796)

 
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
    • Android SDK at /Users/herbert/dev/android/sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-28, build-tools 28.0.3
    • Java binary at: /Users/herbert/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/183.5522156/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 10.2.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 10.2.1, Build version 10E1001
    • CocoaPods version 1.7.3

[✓] iOS tools - develop for iOS devices
    • ios-deploy 1.9.4

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 3.4)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 36.1.1
    • Dart plugin version 183.6270
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)

[✓] Android Studio (version 3.4)
    • Android Studio at /Users/herbert/Library/Application Support/JetBrains/Toolbox/apps/AndroidStudio/ch-0/183.5522156/Android Studio.app/Contents
    • Flutter plugin version 36.1.1
    • Dart plugin version 183.6270
    • Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1343-b01)

[!] IntelliJ IDEA Ultimate Edition (version 2019.1.3)
    • IntelliJ at /Users/herbert/Applications/JetBrains Toolbox/IntelliJ IDEA Ultimate.app
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
    • Dart plugin version 191.7830
    • For information about installing plugins, see
      https://flutter.dev/intellij-setup/#installing-the-plugins

[!] VS Code (version 1.33.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    ✗ Flutter extension not installed; install from
      https://marketplace.visualstudio.com/items?itemName=Dart-Code.flutter

[✓] Connected device (3 available)
    • iPhone Xʀ • D78F2299-D9F1-48CD-957C-A5118243E1A9 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-12-2 (simulator)
    • macOS     • macOS                                • darwin-x64     • Mac OS X 10.14.5 18F132
    • Chrome    • chrome                               • web-javascript • Google Chrome 76.0.3809.46 beta

```