Make the VM's dart:core and dart:async library patches clean.

runtime/lib/core_patch.dart

Index: runtime/lib/core_patch.dart
diff --git a/runtime/lib/core_patch.dart b/runtime/lib/core_patch.dart
index 29357aec4d8fe7c873d5323cb5646c592c3cf382..fbcfdb9012985fcddca78ffe736dcc55d3e2b90b 100644
--- a/runtime/lib/core_patch.dart
+++ b/runtime/lib/core_patch.dart
@@ -25,16 +25,16 @@ class _EnumHelper {
 // implement sync* generator functions. A sync* generator allocates
 // and returns a new _SyncIterable object.
 
-typedef bool SyncGeneratorCallback(Iterator iterator);
+typedef bool _SyncGeneratorCallback(Iterator iterator);
 
 class _SyncIterable extends IterableBase {
-  // moveNextFn is the closurized body of the generator function.
-  final SyncGeneratorCallback moveNextFn;
+  // _moveNextFn is the closurized body of the generator function.
+  final _SyncGeneratorCallback _moveNextFn;
 
-  const _SyncIterable(this.moveNextFn);
+  const _SyncIterable(this._moveNextFn);
 
   get iterator {
-    return new _SyncIterator(moveNextFn._clone());
+    return new _SyncIterator(_moveNextFn._clone());
   }
 }
 
@@ -42,16 +42,16 @@ class _SyncIterator implements Iterator {
   bool isYieldEach;  // Set by generated code for the yield* statement.
   Iterator yieldEachIterator;
   var _current;  // Set by generated code for the yield and yield* statement.
-  SyncGeneratorCallback moveNextFn;
+  _SyncGeneratorCallback _moveNextFn;
 
   get current => yieldEachIterator != null
       ? yieldEachIterator.current
       : _current;
 
-  _SyncIterator(this.moveNextFn);
+  _SyncIterator(this._moveNextFn);
 
   bool moveNext() {
-    if (moveNextFn == null) {
+    if (_moveNextFn == null) {
       return false;
     }
     while(true) {
@@ -62,9 +62,9 @@ class _SyncIterator implements Iterator {
         yieldEachIterator = null;
       }
       isYieldEach = false;
-      // moveNextFn() will update the values of isYieldEach and _current.
-      if (!moveNextFn(this)) {
-        moveNextFn = null;
+      // _moveNextFn() will update the values of isYieldEach and _current.
+      if (!_moveNextFn(this)) {
+        _moveNextFn = null;
         _current = null;
         return false;
       }