[WEB-16445] When create a missing imported library/part, add the edit once.

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

Index: pkg/analysis_server/lib/src/services/correction/fix_internal.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
index cf8676db313a2ee6fedf1b343fbdb9f12dd7d2a7..1b83ef5b6433a07eb420d5832eb948db48822958 100644
--- a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
+++ b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -922,7 +922,6 @@ class FixProcessor {
           String libName = removeEnd(source.shortName, '.dart');
           libName = libName.replaceAll('_', '.');
           SourceEdit edit = new SourceEdit(0, 0, 'library $libName;$eol$eol');
-          change.addEdit(file, -1, edit);
           doSourceChange_addSourceEdit(change, context, source, edit);
         }
         _addFix(DartFixKind.CREATE_FILE, [file]);
@@ -1127,7 +1126,6 @@ class FixProcessor {
         String file = source.fullName;
         String libName = unitLibraryElement.name;
         SourceEdit edit = new SourceEdit(0, 0, 'part of $libName;$eol$eol');
-        change.addEdit(file, -1, edit);
         doSourceChange_addSourceEdit(change, context, source, edit);
         _addFix(DartFixKind.CREATE_FILE, [file]);
       }