Clean up dart:io warnings/errors found by analyzer tests.

sdk/lib/io/link.dart

Index: sdk/lib/io/link.dart
diff --git a/sdk/lib/io/link.dart b/sdk/lib/io/link.dart
index 4fc0312b0fd9b0287aa1475c5fa3d5ebecac4fc2..94250bcd940329a66da2b322e406be73c16a0911 100644
--- a/sdk/lib/io/link.dart
+++ b/sdk/lib/io/link.dart
@@ -177,7 +177,7 @@ class _Link extends FileSystemEntity implements Link {
     if (!(target.length > 3 && target[1] == ':' && target[2] == '\\')) {
       try {
         target = new File(target).fullPathSync();
-      } catch (e) {
+      } on FileException catch (e) {
         throw new LinkException('Could not locate target', target, e.osError);
       }
     }