Provide an API to dart:developer to control the web server hosting the Service Protocol

CHANGELOG.md

 ## 1.21.0
 
 ### Language
 
 * Allow `=` as well as `:` as separator for named parameter default values.
 
+### Service protocol changes

[kevmoo, 2016/10/19 22:26:56]

Thanks!

+
+* Accessing the service protocol now requires prefixing paths with an
+authentication token that can be scrapped from standard output.
+
+```
+Old base url:
+
+Observatory listening on http://127.0.0.1:54804/
+
+New base url:
+
+Observatory listening on http://127.0.0.1:54804/<token>/
+
+For example:
+
+Observatory listening on http://127.0.0.1:54804/PTwjm8Ii8qg=/
+```
+
+* The service protocol http server can now be controlled from the 

[kevmoo, 2016/10/19 22:26:56]

Please add this under new `Core library changes` section after the language
section.

See previous releases for an example

+ `dart:developer` library.
+
 ## 1.20.1 - 2016-10-13
 
 Patch release, resolves one issue:
 
 * Dartium: Fixes a bug that caused crashes.  No issue filed
 
 ## 1.20.0 - 2016-10-11
 
 ### Dart VM
 
@@ skipping 1324 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.