Fix barback-server when seeing a non-ascii error string.

sdk/lib/_internal/pub/lib/src/barback/server.dart

Index: sdk/lib/_internal/pub/lib/src/barback/server.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/server.dart b/sdk/lib/_internal/pub/lib/src/barback/server.dart
index cb6c46eb364118de5dc42c1230f0bc46a8e92aa9..ab8f121d809d3f0cd49eda97d988c4bfe58bcfae 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/server.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/server.dart
@@ -88,6 +88,10 @@ class BarbackServer {
       return;
     }
 
+    // Set content-type to force UTF-8 encoding.
+    request.response.headers.contentType =
+        ContentType.parse("text/html; charset=utf-8");

[Bob Nystrom, 2014/01/09 20:58:11]

Won't this affect anyone doing HTTP in Dart who puts an error message in a
response? Is there a way we can handle this at a lower level in the platform so
other developers benefit too?

[nweiz, 2014/01/09 21:01:27]

If this is only for error-handling, we should move it into [_notFound]. Also,
the content type shouldn't be HTML, since the messages aren't being sent in HTML
(and in fact may have HTML-sensitive characters).

[Anders Johnsen, 2014/01/10 08:52:27]

HTTP requests/responses uses Latin1 by default. That's not something we can
change (it's part of the spec).

However, if you feel like making UTF8 default at a broad level, all you have to
do it set the content-type when you first see the request.

About 'text/html', yes, that may be the wrong mime-type. Depending on what
responses you want to return in UTF-8 (anything with localized errors or paths),
it could be moved accordingly. 

I'll leave it to you to decide where you want it, and what mime-type you prefer.
This CL was mainly for fixing the initial error and getting the tests running
again on the buildbots.

+
     if (request.method != "GET" && request.method != "HEAD") {
       _methodNotAllowed(request);
       return;