Add Changelog entry for CL 1710593002

CHANGELOG.md

 ## 1.15.0
 
 ### 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 an additional option in an `options` file:
   ```yaml
   analyzer:
     language:
@@ skipping 17 matching lines @@
     `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.
 
+### Service protocol changes
+
+* Fixed a documentation bug where the field `extensionRPCs` in `Isolate`
+  was not marked optional.
+
 ## 1.14.2 - 2016-02-09
 
 * Fixes a bug where pub would download packages from pub.dartlang.org even when
   a different hosted URL was specified.
 
 ## 1.14.1 - 2016-02-04
 
 Patch release, resolves one issue:
 
 * Debugger: Fixes a VM crash when a debugger attempts to set a break point
@@ skipping 756 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.