Update changelog for event changes in dart:html

CHANGELOG.md

Index: CHANGELOG.md
diff --git a/CHANGELOG.md b/CHANGELOG.md
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@@ -14,10 +14,92 @@
 
   * Introduce `ChunkedConverter` and deprecate chunked methods on `Converter`.
 
+* `dart:html`
+
+  There have been a number of **BREAKING** changes to align APIs with recent
+  changes in Chrome. These include:
+
+  * Chrome's `ShadowRoot` interface no longer has the methods `getElementById`,
+    `getElementsByClassName`, and `getElementsByTagName`, e.g.,
+
+    ```dart
+    elem.shadowRoot.getElementsByClassName('clazz')
+    ```
+
+    should become:
+
+    ```dart
+    elem.shadowRoot.querySelectorAll('.clazz')
+    ```
+
+  * The `clipboardData` property has been removed from `KeyEvent`
+    and `Event`. It has been moved to the new `ClipboardEvent` class, which is
+    now used by `copy`, `cut`, and `paste` events.
+
+  * The `layer` property has been removed from `KeyEvent` and
+    `UIEvent`. It has been moved to `MouseEvent`.
+
+  * The `Point get page` property has been removed from `UIEvent`.
+    It still exists on `MouseEvent` and `Touch`.
+
+  There have also been a number of other additions and removals to `dart:html`,
+  `dart:indexed_db`, `dart:svg`, `dart:web_audio`, and `dart:web_gl` that
+  correspond to changes to Chrome APIs between v39 and v45. Many of the breaking
+  changes represent APIs that would have caused runtime exceptions when compiled
+  to Javascript and run on recent Chrome releases.
+
 * `dart:io`
   * Added `SecurityContext.alpnSupported`, which is true if a platform
     supports ALPN, and false otherwise.
 
+### JavaScript interop
+
+For performance reasons, a potentially **BREAKING** change was added for
+libraries that use JS interop.
+Any Dart file that uses `@JS` annotations on declarations (top-level functions,
+classes or class members) to interop with JavaScript code will require that the
+file have the annotation `@JS()` on a library directive.
+
+```dart
+@JS()
+library my_library;
+```
+
+The analyzer will enforce this by generating the error:
+
+The `@JS()` annotation can only be used if it is also declared on the library
+directive.
+
+If part file uses the `@JS()` annotation, the library that uses the part should
+have the `@JS()` annotation e.g.,
+
+```dart
+// library_1.dart
+@JS()
+library library_1;
+
+import 'package:js/js.dart';
+
+part 'part_1.dart';
+```
+
+```dart
+// part_1.dart
+part of library_1;
+
+@JS("frameworkStabilizers")
+external List<FrameworkStabilizer> get frameworkStabilizers;
+```
+
+If your library already has a JS module e.g.,
+
+```dart
+@JS('array.utils')
+library my_library;
+```
+
+Then your library will work without any additional changes.
+
 ### Analyzer
 
 *   Static checking of `for in` statements. These will now produce static