Roll Dart back to 1.25.0-dev.6.0

goderbauer · goderbauer · commit 3798ccf63c19 · 2017-07-24T13:21:23.000-07:00
Due to dart-lang/sdk#30210.
diff --git a/bin/internal/dart-sdk.version b/bin/internal/dart-sdk.version
@@ -1 +1 @@
-1.25.0-dev.7.0
+1.25.0-dev.6.0
