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
+
+* Accessing the service protocol now requires a randomly generated path
+prefix to be used. This path prefix can be scraped from standard output
+like the hostname and port are today.
+
+```
+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=/
+
+To connect over WebSocket you would use the following URI:
+
+ws://127.0.0.1:54804/PTwjm8Ii8qg=/ws
+```
+
+### Core library changes

[kevmoo, 2016/10/20 17:21:55]

Forgive me – put this section up below Language. Thanks

[Cutch, 2016/10/20 23:31:51]

Done.

+
+* `dart:developer`
+  * The service protocol http server can now be controlled from Dart code.
+
 ## 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.