Changes in polymer-expressions to prepare for codegen in polymer:

pkg/polymer_expressions/CHANGELOG.md

Index: pkg/polymer_expressions/CHANGELOG.md
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+# changelog
+
+This file contains highlights of what changes on each version of the
+polymer_expressions package.
+
+#### Pub version 0.10.0-dev
+  * package:polymer_expressions no longer declares @MirrosUsed. The package uses
+    mirrors at development time, but assumes frameworks like polymer will
+    generate code that replaces the use of mirrors. If you use this directly,
+    you might need to do code generation as well, or add the @MirrorsUsed
+    declaration. This can be done either explicitly or by importing the old
+    settings from 'package:observe/mirrors_used.dart' (which include
+    @reflectable and @observable by default).
+
+  * Errors that occur within bindings are now thrown asycnhronously. We used to
+    trap some errors and report them in a Logger, and we would let other errors
+    halt the rendering process. Now all errors are caught, but they are reported
+    asynchornously so they are visible even when logging is not set up.