Don't create unused OSError in Socket_Available.

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index d598e273825b799e08ea8fed332508482b1d43c3..d2dfc1433a2d7dd884e720baf89d99bd1817b54b 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -744,14 +744,7 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
           if (isListening) {
             available++;
           } else {
-            var avail = nativeAvailable();
-            if (avail is int) {
-              available = avail;
-            } else {
-              // Available failed. Mark socket as having data, to ensure read
-              // events, and thus reporting of this error.
-              available = 1;
-            }
+            available = nativeAvailable();
             issueReadEvent();
             continue;
           }