Repository: flutter
Issue: [google_maps_flutter_web] [web] onMapCreated not called with AnimatedOpacity
Labels: engine,a: platform-views,p: maps,platform-web,package,has reproducible steps,P2,c: parity,found in release: 2.5,found in release: 2.6,team-web,triaged-web


## Steps to Reproduce
Here is the basic gist of showing google maps after its being created.

```
bool isMapVisible = false;

AnimatedOpacity(
  opacity: isMapVisible ? 1.0 : 0,
  duration: Duration(milliseconds: 600),
  child: GoogleMap(
    initialCameraPosition: CameraPosition(
      target: LatLng(
        37.4503622703105, 127.12989966313339),
        zoom: 16,
    ),
    onMapCreated: (GoogleMapController controller) {
      _controller.complete(controller);
      Future.delayed(
          const Duration(milliseconds: 550),
          () => setState(() {isMapVisible = true;}));
    },
))
```
While the above code works for iOS and Android, it fails to run on `flutter web`. 
The `onMapCreated` callback is never called when opacity is set to `0.0` initially.

**Expected results:** <!-- what did you want to see? -->

**Actual results:** <!-- what did you see? -->

<details>
  <summary>flutter doc -v</summary>

```
ahetawal@thatch thatch (main)*$ flutter doctor -v
[✓] Flutter (Channel stable, 2.5.1, on macOS 11.6 20G165 darwin-x64, locale en-US)
    • Flutter version 2.5.1 at /Users/ahetawal/sdk/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision ffb2ecea52 (2 weeks ago), 2021-09-17 15:26:33 -0400
    • Engine revision b3af521a05
    • Dart version 2.14.2

[✓] Android toolchain - develop for Android devices (Android SDK version 31.0.0)
    • Android SDK at /Users/ahetawal/Library/Android/sdk
    • Platform android-31, build-tools 31.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.10+0-b96-7281165)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.5.1, Build version 12E507
    • CocoaPods version 1.11.2

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2020.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 11.0.10+0-b96-7281165)

[✓] IntelliJ IDEA Ultimate Edition (version 2021.2.1)
    • IntelliJ at /Users/ahetawal/Applications/JetBrains Toolbox/IntelliJ IDEA Ultimate.app
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart

[✓] IntelliJ IDEA Ultimate Edition (version 2021.2.1)
    • IntelliJ at /Users/ahetawal/Library/Application Support/JetBrains/Toolbox/apps/IDEA-U/ch-0/212.5080.55/IntelliJ IDEA.app
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart

[✓] VS Code (version 1.59.0)
    • VS Code at /Users/ahetawal/Downloads/Visual Studio Code.app/Contents
    • Flutter extension version 3.26.0

[✓] Connected device (2 available)
    • iPhone 11 Pro (mobile) • EEC598B2-5A92-43AA-8C44-76033FDE5268 • ios            • com.apple.CoreSimulator.SimRuntime.iOS-14-5 (simulator)
    • Chrome (web)           • chrome                               • web-javascript • Google Chrome 94.0.4606.61

• No issues found!
</details>