Handle 'part of' declarations with URI correctly in Fasta.

pkg/front_end/lib/src/fasta/parser/parser.dart

Index: pkg/front_end/lib/src/fasta/parser/parser.dart
diff --git a/pkg/front_end/lib/src/fasta/parser/parser.dart b/pkg/front_end/lib/src/fasta/parser/parser.dart
index 275c3ed762e596c8bcba89250244c25b719282ee..d86c385bb685670587f37f5ba9e566127d014155 100644
--- a/pkg/front_end/lib/src/fasta/parser/parser.dart
+++ b/pkg/front_end/lib/src/fasta/parser/parser.dart
@@ -348,7 +348,8 @@ class Parser {
     assert(optional('of', token.next));
     Token partKeyword = token;
     token = token.next.next;
-    if (token.isIdentifier()) {
+    bool hasName = token.isIdentifier();
+    if (hasName) {
       token = parseQualified(token, IdentifierContext.partName,
           IdentifierContext.partNameContinuation);
     } else {
@@ -356,7 +357,7 @@ class Parser {
     }
     Token semicolon = token;
     token = expect(';', token);
-    listener.endPartOf(partKeyword, semicolon);
+    listener.endPartOf(partKeyword, semicolon, hasName);
     return token;
   }