Don't use [operator==] to refer to [==] in DartDoc. It doesn't work.

sdk/lib/core/string.dart

Index: sdk/lib/core/string.dart
diff --git a/sdk/lib/core/string.dart b/sdk/lib/core/string.dart
index 39641df87e5439b414095eed8f9d017a9d4b0d71..40d87bf5381e660d11dc6f9b449f05f4c6f40144 100644
--- a/sdk/lib/core/string.dart
+++ b/sdk/lib/core/string.dart
@@ -187,7 +187,7 @@ abstract class String implements Comparable<String>, Pattern {
   /**
    * Returns a hash code derived from the code units of the string.
    *
-   * This is compatible with [operator==]. Strings with the same sequence
+   * This is compatible with [==]. Strings with the same sequence
    * of code units have the same hash code.
    */
   int get hashCode;