Currently flutter run -d web creates a server with the x-frame-options: SAMEORIGIN added by default (shelf add it's by default). This doesn't allow you to use it inside a frame.

I am trying to build an embedded simulator in vscode and it requires using an iframe.

With this PR I remove the header for debug and profile mode.

Like Android/iOS, only enable --null-assertions if asked. Previously this was enabled by default for web, but in general this has proved to be too breaking to enable by default.

#61042

* Add punctuation for unterminated sentences in doc comments

* Addressing review nit

To support #61407 , the tool needs to check if a single widget reload is feasible, and then conditionally perform a fast reassemble.

To accomplish this, the FlutterDevice class will have a WidgetCache injected. This will eventually contain the logic for parsing the invalidated dart script. Concurrent with the devFS update, the widget cache will be updated/checked if a single widget reload is feasible. If so, an expression evaluation with the target type is performed and the success is communicated through the devFS result. An integration test which demonstrates that this works is already present in https://github.com/flutter/flutter/blob/master/packages/flutter_tools/test/integration.shard/hot_reload_test.dart#L86

Finally, when actually performing the reassemble the tool simply checks if this flag has been set and calls the alternative reassemble method.

Cleanups:

Remove modules, as this is unused now.

Enable null safety asserts for web debug mode. This induces runtime asserts at the boundaries between null safe and non-null safe libraries. Adds integration test that validates assertion error is thrown.

#61042

Made flutter tools serve metadata produced by the frontend server:

pass --experimental-emit-metadata flag to flutter engine
store and serve metadata from web asset server
store and serve merged metadata from web asset server
add tests to verify that metadata is served from memory
update dwds version so it can read metadata
configure dwds to read metadata from file
Prerequisite changes (landed):

sdk: https://dart-review.googlesource.com/c/sdk/+/150181
flutter engine: flutter/engine#19168
webdev:dart-lang/webdev#1064

In web debug mode, infer sound null safety by default. When sound null safety is enabled, provide a separate dill and precompiled Dart SDK. Release builds do not need this setting since we run dart2js from source.

Fixes #59873

The global packages path could cause tests to fail when it would be overriden to unexpected (in test setup) values. Remove most usage and make it a configuration on buildInfo, along with most other build information. Cleanup the asset builder to require the .packages path and the resident runners to no longer require it, since they already have the information in build_info.

It needs to stick around for the fuchsia deps we do not control.

Filled #60232 for remaining work.

WebAssetServer could fail if some of the global statics it depended on were initialized in a different order. Fix this by removing globals.

Delete dwds startup test that needs to spawn a real server.

Fixes additional bugs uncovered by tester, style fixes to prevent suggested imports.

Fixes #59718

Update all versions, specifically dwds which has a hot restart fix

[flutter_tools] set test directory base as additional root, allow running without index.html (#55531)

Should fix issues introduced in web-server device and allow loading org-dartlang-app URIs

Update to latest dwds APIs, moving back to dwds driven hot restart and enabling future work on expression evaluation.

This is required to roll forward package:vm_service to 3.0.0 and is
blocking a DevTools release.