Fix continue in invalidation logic

When invalidating changed files in frontend server, the state prior to
this CL was that a continue would jump to the next byte, not the next file
after it had seen that the file had changed. Thus it could possibly
invalidate the same file several times.

Change-Id: If6fb1042248d26a3ffe905b39fa3c3603198ca37
Reviewed-on: https://dart-review.googlesource.com/60245
Commit-Queue: Jens Johansen <[email protected]>
Reviewed-by: Aske Simon Christensen <[email protected]>

Author: jensjoha

pkg/vm/lib/frontend_server.dart

@@ -385,25 +385,26 @@ class FrontendCompiler implements CompilerInterface {
       return null;
     }
 
+    nextUri:
     for (Uri uri in component.uriToSource.keys) {
-      if (uri == null || '$uri' == '') continue;
+      if (uri == null || '$uri' == '') continue nextUri;
 
       final List<int> oldBytes = component.uriToSource[uri].source;
       final FileSystemEntity entity =
           _compilerOptions.fileSystem.entityForUri(uri);
       if (!await entity.exists()) {
         _generator.invalidate(uri);
-        continue;
+        continue nextUri;
       }
       final List<int> newBytes = await entity.readAsBytes();
       if (oldBytes.length != newBytes.length) {
         _generator.invalidate(uri);
-        continue;
+        continue nextUri;
       }
       for (int i = 0; i < oldBytes.length; ++i) {
         if (oldBytes[i] != newBytes[i]) {
           _generator.invalidate(uri);
-          continue;
+          continue nextUri;
         }
       }
     }