Polymer transformer logs now show on the frontend for pub serve.

pkg/polymer/CHANGELOG.md

 # changelog
 
 This file contains highlights of what changes on each version of the polymer
 package. We will also note important changes to the polyfill packages (observe,
 web_components, and template_binding) if they impact polymer.
 
 #### Pub version 0.12.1-dev
   * Added the ability to override the stylesheet inlining behavior. There is now
     an option exposed in the pubspec.yaml called `inline_stylesheets`. There are
     two possible values, a boolean or a map. If only a boolean is supplied then
     that will set the global default behavior. If a map is supplied, then the
     keys should be file paths, and the value is a boolean. You can use the
     special key 'default' to set the default value.
 
     For example, the following would change the default to not inline any
     styles, except for the foo.css file in your web folder and the bar.css file
     under the foo packages lib directory:
 
         inline_stylesheets:
             default: false
             web/foo.css: true
             packages/foo/bar.css: true
 
+  * Added `inject_build_logs_in_output` option to pubspec for polymer
+    transformers. When set to `true`, this will inject a small element into your
+    entry point pages that will display all log messages from the polymer
+    transformers during the build step. This element is only injected when not 
+    running in release mode (ie: `pub serve` but not `pub build`).
+
 #### Pub version 0.12.0+7
   * Widen the constraint on `unittest`.
 
 #### Pub version 0.12.0+6
   * Widen the constraint on analyzer.
   * Support for `_src` and similar attributes in polymer transformers.
 
 #### Pub version 0.12.0+5
   * Raise the lower bound on the source_maps constraint to exclude incompatible
     versions.
@@ skipping 110 matching lines @@
 #### Pub version 0.9.2+3
   * fix [15574](https://code.google.com/p/dart/issues/detail?id=15574),
     event bindings in dart2js, by working around issue
     [15573](https://code.google.com/p/dart/issues/detail?id=15573)
 
 #### Pub version 0.9.2+2
   * fix enteredView in dart2js, by using custom_element >= 0.9.1+1
 
 [6ad2d61]:https://github.com/Polymer/polymer-dev/commit/6a3e1b0e2a0bbe546f6896b3f4f064950d7aee8f
 [3b690ad]:https://github.com/Polymer/polymer-dev/commit/3b690ad0d995a7ea339ed601075de2f84d92bafd