Add CHANGELOG entries for Dartium and dart:html changes

CHANGELOG.md

 ## 1.14.0
 
 ### Core library changes
 * `dart:math`
   * `Random` added a `secure` constructor returning a cryptographically secure
     random generator which reads from the entropy source provided by the
     embedder for every generated random value.
 
 ## 1.13.0
 
@@ skipping 14 matching lines @@
 
 * `dart:core`
   * `Uri` added `removeFragment` method.
   * `String.allMatches` (implementing `Pattern.allMatches`) is now lazy,
     as all `allMatches` implementations are intended to be.
   * `Resource` is deprecated, and will be removed in a future release.
 
 * `dart:developer`
   * Added `Timeline` class for interacting with Observatory's timeline feature.
   * Added `ServiceExtensionHandler`, `ServiceExtensionResponse`, and `registerExtension` which enable developers to provide their own VM service protocol extensions.
-  
+
+* `dart:html`, `dart:indexed_db`, `dart:svg`, `dart:web_audio`, `dart:web_gl`, `dart:web_sql`
+  * The return type of some APIs changed from `double` to `num`. Dartium is now
+    using
+    JS interop for most operations. JS does not distinguish between numeric
+    types, and will return a number as an int if it fits in an int. This will
+    mostly cause an error if you assign to something typed `double` in
+    checked mode. You may
+    need to insert a `toDouble()` call or accept `num`. Examples of APIs that
+    are affected include `Element.getBoundingClientRect` and
+    `TextMetrics.width`.
+
 * `dart:io`
   * **Breaking:** Secure networking has changed, replacing the NSS library
     with the BoringSSL library. `SecureSocket`, `SecureServerSocket`,
     `RawSecureSocket`,`RawSecureServerSocket`, `HttpClient`, and `HttpServer`
     now all use a `SecurityContext` object which contains the certificates
     and keys used for secure TLS (SSL) networking.
 
     This is a breaking change for server applications and for some client
     applications. Certificates and keys are loaded into the `SecurityContext`
     from PEM files, instead of from an NSS certificate database. Information
@@ skipping 20 matching lines @@
 * `docgen` and 'dartdocgen' no longer ship in the sdk. The `docgen` sources have
    been removed from the repository.
 
 * This is the last release to ship the VM's "legacy debug protocol".
   We intend to remove the legacy debug protocol in Dart VM 1.14.
 
 * The VM's Service Protocol has been updated to version 3.0 to take care
   of a number of issues uncovered by the first few non-observatory
   clients.  This is a potentially breaking change for clients.
 
+* Dartium has been substantially changed. Rather than using C++ calls into
+  Chromium internals for DOM operations it now uses JS interop.
+  The DOM objects in `dart:html` and related libraries now wrap
+  a JavaScript object and delegate operations to it. This should be
+  mostly transparent to users. However, performance and memory characteristics
+  may be different from previous versions. There may be some changes in which
+  DOM objects are wrapped as Dart objects. For example, if you get a reference
+  to a Window object, even through JS interop, you will always see it as a
+  Dart Window, even when used cross-frame. We expect the change to using
+  JS interop will make it much simpler to update to new Chrome versions.
+
 ## 1.12.2 - 2015-10-21
 
 ### Core library changes
 
 * `dart:io`
 
   * A memory leak in creation of Process objects is fixed.
 
 ## 1.12.1 - 2015-09-08
 
@@ skipping 536 matching lines @@
     they will keep the Dart process alive until they time out. This fixes the
     handling of persistent connections. Previously, the client would shut down
     immediately after a request.
 
   * **Breaking change:** `HttpServer` no longer compresses all traffic by
     default. The new `autoCompress` property can be set to `true` to re-enable
     compression.
 
 * `dart:isolate`: `Isolate.spawnUri` added the optional `packageRoot` argument,
   which controls how it resolves `package:` URIs.