Repository: flutter
Issue: [web][Chrome] Back button isn't enabled in a fresh tab with no history
Labels: framework,f: routes,platform-web,has reproducible steps,P2,found in release: 3.7,found in release: 3.8,team-web,triaged-web

## Steps to Reproduce

Adding a local history entry does not enable the back button in the browser.

Here's a sample app:
https://github.com/carloshwa/flutter-example/tree/local_history

It is the default sample app modified so the FAB adds its action to local history:
https://github.com/carloshwa/flutter-example/blob/3493314124bd29a75f9c4e3e6224e520add5126e/myapp/lib/main.dart#L56-L60

When run on Android, the device back button is able to decrement the counter. But in a web browser, the back button does not get enabled when `addLocalHistoryEntry()` gets called.

The curious thing is if the browser's back button is *already* enabled (because the current browsing session already has a history), it does behave correctly.

Tested on Chrome macOS 83.0.4103.97.

**Expected results:**
Browser back button is enabled when `addLocalHistoryEntry()` is called.

**Actual results:**
Browser back button remains disabled when `addLocalHistoryEntry()` is called.

<details>
  <summary>flutter doctor -v</summary>

```
[✓] Flutter (Channel beta, 1.19.0-4.1.pre, on Mac OS X 10.15.5 19F101, locale en-US)
    • Flutter version 1.19.0-4.1.pre at /Users/panda/pandamonium/flutter
    • Framework revision f994b76974 (2 days ago), 2020-06-09 15:53:13 -0700
    • Engine revision 9a28c3bcf4
    • Dart version 2.9.0 (build 2.9.0-14.1.beta)

[!] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /Users/panda/android-sdk
    • Platform android-29, build-tools 29.0.3
    • ANDROID_HOME = /Users/panda/android-sdk
    • Java binary at: /Applications/Android Studio 4.0.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
    ✗ Android license status unknown.
      Try re-installing or updating your Android SDK Manager.
      See https://developer.android.com/studio/#downloads or visit https://flutter.dev/docs/get-started/install/macos#android-setup
      for detailed instructions.

 
[✓] Xcode - develop for iOS and macOS (Xcode 11.4.1)
    • Xcode at /Applications/Xcode 11.4.app/Contents/Developer
    • Xcode 11.4.1, Build version 11E503a
    • CocoaPods version 1.9.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[!] Android Studio (version 3.5)
    • Android Studio at /Applications/Android Studio 3.5.app/Contents
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
    ✗ Dart plugin not installed; this adds Dart specific functionality.
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[!] Android Studio (version 4.0)
    • Android Studio at /Applications/Android Studio 4.0.app/Contents
    ✗ Flutter plugin not installed; this adds Flutter specific functionality.
    ✗ Dart plugin not installed; this adds Dart specific functionality.
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)

[✓] IntelliJ IDEA Community Edition (version 2020.1.2)
    • IntelliJ at /Applications/IntelliJ IDEA CE.app
    • Flutter plugin version 46.0.3
    • Dart plugin version 201.7846.93

[✓] Connected device (2 available)
    • Web Server • web-server • web-javascript • Flutter Tools
    • Chrome     • chrome     • web-javascript • Google Chrome 83.0.4103.97

! Doctor found issues in 3 categories.
```

</details>