Fix a number of issues with the Range header handling for serving files

pkg/http_server/test/http_mock.dart

 library http_mock;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:io';
 
 class MockHttpHeaders implements HttpHeaders {
   final Map<String, List<String>> _headers =
       new HashMap<String, List<String>>();
 
+  operator[](key) => _headers[key];
+
+  int get contentLength => int.parse(_headers[HttpHeaders.CONTENT_LENGTH][0]);
 
   DateTime get ifModifiedSince {
     List<String> values = _headers[HttpHeaders.IF_MODIFIED_SINCE];
     if (values != null) {
       try {
         return HttpDate.parse(values[0]);
       } on Exception catch (e) {
         return null;
       }
     }
@@ skipping 68 matching lines @@
     assert(name == name.toLowerCase());
     List<String> values = new List<String>();
     _headers[name] = values;
     values.add(value);
   }
 
   /*
    * Implemented to remove editor warnings
    */
   dynamic noSuchMethod(Invocation invocation) {
-    print([invocation.memberName, invocation.isGetter, invocation.isSetter, invocation.isMethod, invocation.isAccessor]);
+    print([invocation.memberName,
+           invocation.isGetter,
+           invocation.isSetter,
+           invocation.isMethod,
+           invocation.isAccessor]);
     return super.noSuchMethod(invocation);
   }
 }
 
 class MockHttpRequest implements HttpRequest {
   final Uri uri;
   final MockHttpResponse response = new MockHttpResponse();
   final HttpHeaders headers = new MockHttpHeaders();
   final String method = 'GET';
   final bool followRedirects;
@@ skipping 64 matching lines @@
   }
 
   /*
    * Implemented to remove editor warnings
    */
   dynamic noSuchMethod(Invocation invocation) =>
       super.noSuchMethod(invocation);
 
   String get mockContent => UTF8.decode(_buffer);
 
+  List<int> get mockContentBinary => _buffer;
+
   bool get mockDone => _isDone;
 
   // Copied from SDK http_impl.dart @ 845 on 2014-01-05
   // TODO: file an SDK bug to expose this on HttpStatus in some way
   String _findReasonPhrase(int statusCode) {
     if (_reasonPhrase != null) {
       return _reasonPhrase;
     }
 
     switch (statusCode) {
       case HttpStatus.NOT_FOUND: return "Not Found";
       default: return "Status $statusCode";
     }
   }
 }