Source positions for constructors and lots of async machinery

runtime/vm/scanner.h

Index: runtime/vm/scanner.h
diff --git a/runtime/vm/scanner.h b/runtime/vm/scanner.h
index 7a8104081f3408be2f712ef00d0fdac7eeb1f3dc..5b35317e9d0a4271b6e3370bd4e7bdc860229e4c 100644
--- a/runtime/vm/scanner.h
+++ b/runtime/vm/scanner.h
@@ -44,13 +44,6 @@ class Scanner : ValueObject {
     const String* literal;    // Identifier, number or string literal.
   };
 
-  // Dummy token index reflecting an unknown source position.
-  static const intptr_t kNoSourcePos = -1;
-
-  static bool ValidSourcePosition(intptr_t token_pos) {
-    return (token_pos >= 0) || (token_pos == kNoSourcePos);
-  }
-
   typedef ZoneGrowableArray<TokenDescriptor> GrowableTokenStream;
 
   // Initializes scanner to scan string source.