This adds a check for the presence of dart2js in the engine build.
Felt relies on an engine build with `--full-dart-sdk` set. Previously,
we checked for the presence of pub, but not for the presence of
web-specific tooling such as dart2js that felt relies on. Pub is built
as part of the default Dart SDK build when `--full-dart-sdk` is not set,
so its presence is insufficient to prove that other required tooling is
present.
Without this check, we get the following error on run:
Unhandled exception:
ProcessException: No such file or directory
Command: /Users/cbracken/src/flutter/engine/src/out/host_debug_unopt/dart-sdk/bin/dart2js --no-minify --disable-inlining --enable-asserts --enable-experiment=non-nullable --no-sound-null-safety -O2 -o test/paragraph_builder_test.dart.browser_test.dart.js test/paragraph_builder_test.dart
* adding arguments to felt for running different type of tests
* adding test type enums to felt
* more changes to felt for testing branches
* more additions to code
* more changes to felt
* adding code for cloning web_drivers
* validating test directories. running the integration tests. update the readme file partially
* Removing todo lists used for development
* addressing reviewers comments
* remove unused imports
* addressing more reviewer comments
* addressing more reviewer comments
* addressing reviewer comments.
* addressing reviewer comments.
* fixing typos
* using chromedriverinstaller as a library. Fixing the commit number used from web_installers repo
* clean drivers directory after tests finish
* addressing more reviewer comments
* throwing all critical exceptions instead of logging and returning boolean flags
* adding todos for items we can do for making felt easier to use for local development
* do not run integration tests on CIs. Added an issue to the TODO.
* changing todo's with issues.
1. Various functionalities offered by this tool are now organized into commands (e.g. `felt test`, `felt check-licenses`).
2. The felt tool can now be invoked from anywhere, not necessarily from the web_ui directory.
3. This new structure helps us scale better as we add more commands (e.g. soon a `build/watch` command is coming).
