Cleaned up a few entries in the CHANGELOG

Mostly addressing my comments on https://dart-review.googlesource.com/c/sdk/+/67860 for the dart2js section

Change-Id: I421489088ba79be693fa07662a7c008f1f950944
Reviewed-on: https://dart-review.googlesource.com/68160
Reviewed-by: Vijay Menon <[email protected]>
Commit-Queue: Sigmund Cherem <[email protected]>

Author: sigmundch

CHANGELOG.md

@@ -104,7 +104,7 @@ significant changes across all areas of the platform. Large changes include:
     }
     ```
 
-*   Bounds on generic functions are invariant The following program now issues
+*   Bounds on generic functions are invariant. The following program now issues
     an invalid override error ([issue 29014][sdk#29014]):
 
     ```dart
@@ -391,7 +391,7 @@ Still need entries for all changes to dart:html since 1.x
     null, which is a value that was always possible for it to return previously.
 *   Deprecated `packageRoot` parameter in `Isolate.spawnUri`, which is was
     previously used only for `packages/` directory resolution. That style of
-    resolution is no longer supported in dart 2.
+    resolution is no longer supported in Dart 2.
 
 <!--
 Still need entries for all changes to dart:js since 1.x
@@ -406,8 +406,9 @@ Still need entries for all changes to dart:js since 1.x
 
 *   Added `IsolateMirror.loadUri`, which allows dynamically loading additional
     code.
-*   Marked `MirrorsUsed` as deprecated. The mirrors library is no longer
-    supported by dart2js, and `MirrorsUsed` only affected dart2js.
+*   Marked `MirrorsUsed` as deprecated. The `MirrorsUsed` annotation was only
+    used to inform the dart2js compiler about how mirrors were used, but dart2js
+    no longer supports the mirrors library altogether.
 
 <!--
 Still need entries for all changes to dart:svg since 1.x
@@ -435,13 +436,13 @@ Still need entries for all changes to dart:web_audio,web_gl,web_sql since 1.x
     https://github.com/dart-lang/sdk/blob/master/docs/language/informal/int64.md
     for details.
 
-*   The dart VM no longer attempts to perform `packages/` directory resolution
+*   The Dart VM no longer attempts to perform `packages/` directory resolution
     (for loading scripts, and in `Isolate.resolveUri`). Users relying on
     `packages/` directories should switch to `.packages` files.
 
 ### Dart for the Web
 
-*   Expose Javascript Promise APIs using Dart futures. For example,
+*   Expose JavaScript Promise APIs using Dart futures. For example,
     `BackgroundFetchManager.get` is defined as:
 
     ```dart
@@ -481,60 +482,35 @@ Still need entries for all changes to dart:web_audio,web_gl,web_sql since 1.x
 
 #### dart2js
 
-*   The dart2js compiler now uses the common front-end by default. This is a
-    step towards supporting Dart 2.0. At this time dart2js has no semantic
-    changes: the Dart 2.0 strong-mode semantics are not enabled, so dart2js
-    continues to support the Dart 1 type system. This change however lets us
-    start supporting new syntactic features of Dart 2.0, like optional
-    new/const. With this change you may notice:
+*   dart2js now compiles programs with Dart 2.0 semantics. Apps are expected to
+    be bigger than before, because Dart 2.0 has many more implicit checks
+    (similar to the `--checked` flag in Dart 1.0).
 
-    *   Small code differences (~1% code size): some code is generated slightly
-        different, this is expected because the internal representation of the
-        program has small differences between the old and new front end.
+    We exposed a `--omit-implicit-checks` flag which removes most of the extra
+    implicit checks. Only use this if you have enough test coverage to know that
+    the app will work well without the checks. If a check would have failed and
+    it is omitted, your app may crash or behave in unexpected ways. This flag is
+    similar to `--trust-type-annotations` in Dart 1.0.
 
-    *   Source-maps changes: with the new front-end, dart2js also is using a new
-        mechanism to generate source-map files. We don't expect big differences
-        here either, the new source-maps try to encode more data for locations
-        that are commonly used during debugging.
+*   dart2js replaced its front-end with the common front-end (CFE). Thanks to
+    the CFE, dart2js errors are more consistent with all other Dart tools.
 
-    *   Some missing errors: the CFE is not complete and may not report some
-        static errors that the old front-end did. This is temporary. If you run
-        the analyzer on all your project already, you may never notice those
-        missing error messages.
+*   dart2js replaced its source-map implementation.  There aren't any big
+    differences, but more data is emitted for synthetic code generated by the
+    compiler.
 
-    *   As announced earlier, this is the first version of dart2js that no
-        longer supports `dart:mirrors`.
+*   `dart:mirrors` support was removed. Frameworks are encouraged to use
+    code-generation instead. Conditional imports indicate that mirrors are not
+    supported, and any API in the mirrors library will throw at runtime.
 
-    *   This is the first version of dart2js that no longer supports
-        `--package-root`, which long ago was deprecated in favor of
-        `--packages`.
+*   The generated output of dart2js can now be run as webworker.
 
-*   Fixed `--no-frequency-based-minification`, which was not working together
-    with the common front-end ([issue 32600][sdk#32600]).
-
-*   Support `--categories=Server` with the common front-end. This included also
-    fixes for the constant value `bool.fromEnvironment("*")` of
-    "dart.libraries.io", "dart.libraries.mirrors", "dart.libraries.isolate", and
-    "dart.libraries.html".
-
-*   Several fixes to improve support for running output of dart2js as a
-    webworker.
-
-*   `dart:isolate` implementation removed. To launch background tasks, please
+*   `dart:isolate` support was removed. To launch background tasks, please
     use webworkers instead. APIs for webworkers can be accessed from `dart:html`
     or JS-interop.
 
-*   Dart2js now compiles programs by default with Dart 2.0 semantics. Apps are
-    expected to be bigger than before, because Dart 2.0 has many more implicit
-    checks (similar to the `--checked` flag in Dart 1.0).
-
-*   Add `--omit-implicit-checks` which removes most of the extra implicit
-    checks. Only use this if you have enough test coverage to know that the app
-    will work well without the checks. If a check would have failed and it is
-    omitted, your app may crash or behave in unexpected ways.
-
-[sdk#32561]: https://github.com/dart-lang/sdk/issues/32561
-[sdk#32600]: https://github.com/dart-lang/sdk/issues/32600
+*   dart2js no longer supports the `--package-root` flag. This flag was
+    deprecated in favor of `--packages` long ago.
 
 ### Tool Changes