Change "FormatException.position" to be named "offset".

Address comments on SpanFormatException changes.

R=nweiz@google.com

Committed: https://code.google.com/p/dart/source/detail?r=38373

Committed: https://code.google.com/p/dart/source/detail?r=38378

Review URL: https://codereview.chromium.org//396603003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/source_span@38379 260f80e4-7a28-3924-810f-c04153c831b5

pkgs/source_span/lib/src/span_exception.dart

diff --git a/pkgs/source_span/lib/src/span_exception.dart b/pkgs/source_span/lib/src/span_exception.dart
index af64241..36f2488 100644
--- a/pkgs/source_span/lib/src/span_exception.dart
+++ b/pkgs/source_span/lib/src/span_exception.dart
@@ -36,7 +36,7 @@
     implements FormatException {
   final source;
 
-  int get position => span == null ? null : span.start.offset;
+  int get offset => span == null ? null : span.start.offset;
 
   SourceSpanFormatException(String message, SourceSpan span, [this.source])
       : super(message, span);