Breakpoints are not hit for macos apps after hot restart or hot reload #3359

Repro steps

1. run flutter hello_world app for macos platform:

  cd flutter/flutter/examples/hello_world
  flutter run --debug -d macos

2. run devtools
   pub global run devtools
3. connect devtools to the app by copying and pasting the app debug uri into devtools connection box
4. when source for main.dart is displayed in the debugger screen, put a breakpoint on runApp line and hot restart or hot reload.

Expected
Breakpoint is hit when the app re-runs.

Actual
Breakpoint is not hit. In addition, breakpoint disappears after hot restart.

Versions
Devtools: 2.6.0

flutter doctor -v

➜ hello_world git:(annagrin/update_dwds) ✗ flutter doctor -v
[✓] Flutter (Channel annagrin/update_dwds, 2.6.0-1.0.pre.245, on macOS 11.5.1 20G80
darwin-x64, locale en-US)
• Flutter version 2.6.0-1.0.pre.245 at /Users/annagrin/source/flutter/flutter
• Upstream repository [email protected]:annagrin/flutter.git
• Framework revision 26db5554fd (26 hours ago), 2021-09-09 14:48:19 -0700
• Engine revision 825c409164
• Dart version 2.15.0 (build 2.15.0-93.0.dev)

[!] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
• Android SDK at /Users/annagrin/Library/Android/sdk
✗ cmdline-tools component is missing
Run path/to/sdkmanager --install "cmdline-tools;latest"
See https://developer.android.com/studio/command-line for more details.
✗ Android license status unknown.
Run flutter doctor --android-licenses to accept the SDK licenses.
See https://flutter.dev/docs/get-started/install/macos#android-setup for more
details.

[✓] Xcode - develop for iOS and macOS (Xcode 12.4)
• Xcode at /Applications/Xcode.app/Contents/Developer
• CocoaPods version 1.10.1

[✓] Chrome - develop for the web
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 3.6)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 45.1.1
• Dart plugin version 192.7761
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)

[✓] IntelliJ IDEA Community Edition (version 2021.1)
• IntelliJ at /Applications/IntelliJ IDEA CE.app
• Flutter plugin version 55.1.5
• Dart plugin version 211.6693.108

[✓] VS Code (version 1.59.1)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.25.0

[✓] Connected device (2 available)
• macOS (desktop) • macos • darwin-x64 • macOS 11.5.1 20G80 darwin-x64
• Chrome (web) • chrome • web-javascript • Google Chrome 93.0.4577.63

! Doctor found issues in 1 category.