update changelog for Dartium roll

CHANGELOG.md

 ## 1.15.0
 
 ### Core library changes
 
 * `dart:async`
   * Made `StreamView` class a `const` class.
 
 * `dart:core`
   * Added `Uri.queryParametersAll` to handle multiple query parameters with
     the same name.
 
 * `dart:io`
   * Added `SecurityContext.usePrivateKeyBytes`,
     `SecurityContext.useCertificateChainBytes`,
     `SecurityContext.setTrustedCertificatesBytes`, and
     `SecurityContext.setClientAuthoritiesBytes`.
   * **Breaking** The named `directory` argument of
     `SecurityContext.setTrustedCertificates` has been removed.
   * Added support to `SecurityContext` for PKCS12 certificate and key
     containers.
   * All calls in `SecurityContext` that accept certificate data now accept an
     optional named parameter `password`, similar to
     `SecurityContext.usePrivateKeyBytes`, for use as the password for PKCS12
     data.
 
+### Dartium
+
+  * The Chrome-based tools that ship as part of the Dart SDK – Dartium and
+    content shell – are now based on Chrome version 45 (instead of Chrome 39).
+  * Dart browser libraries (`dart:html`, `dart:svg`, etc) have not been updated.
+    * These are still based on Chrome 39.
+    * These APIs will be updated in a future release.
+  * Note that there are experimental APIs which have changed in the underlying
+    browser, and will not work with the older libraries.
+    For example, `Element.animate`.
+
 ### Service protocol changes
 
 * Fixed a documentation bug where the field `extensionRPCs` in `Isolate`
   was not marked optional.
 
 ### Experimental language features
   * Added support for [configuration-specific imports](https://github.com/munificent/dep-interface-libraries/blob/master/Proposal.md).
     On the VM and `dart2js`, they can be enabled with `--conditional-directives`.
 
     The analyzer requires additional configuration:
@@ skipping 776 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.