Make some VM libraries patch cleanly using the analyzer.

sdk/lib/internal/symbol.dart

Index: sdk/lib/internal/symbol.dart
diff --git a/sdk/lib/internal/symbol.dart b/sdk/lib/internal/symbol.dart
index 64fcdb389118bfa0585010508800802e89da92c5..73e702377d19b3de16de0c48da5f961a6806b9c2 100644
--- a/sdk/lib/internal/symbol.dart
+++ b/sdk/lib/internal/symbol.dart
@@ -114,7 +114,7 @@ class Symbol implements core.Symbol {
 
   external int get hashCode;
 
-  toString() => 'Symbol("$_name")';
+  external toString();

[hausner, 2016/12/14 23:35:40]

Why is it necessary to patch toString()? Isn't the implementation the same for
all platforms?

[Siggi Cherem (dart-lang), 2016/12/15 00:31:46]

It seems like the vm was patching it with some extra conversion to change names
like "set:foo' to 'foo=': 
https://github.com/dart-lang/sdk/blob/master/runtime/lib/symbol_patch.dart#L9

Is the VM patch is no longer necessary?


I also noticed that we are getting some inconsistent results among tools: this
program prints 'foo=' in the VM, and produces compile-time errors in dart2js and
analyzer:

main() {
  print(const Symbol('set:foo'));
}

[Lasse Reichstein Nielsen, 2016/12/15 07:55:41]

That's http://dartbug.com/13596 - the VM isn't validating arguments to the
Symbol constructor.

It's somewhat morally defensible since a const constructor can't really validate
anything, but it could be handled by special-casing.

 
   /// Platform-private accessor which cannot be called from user libraries.
   static String getName(Symbol symbol) => symbol._name;