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

sdk/lib/_internal/js_runtime/lib/core_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/core_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/core_patch.dart b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
index c6aa41e5cd9c76249d1a6ec302789925e6563000..2b1ae39227e8c2de659a73f457e3149544c367ae 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -47,6 +47,9 @@ int identityHashCode(Object object) => objectHashCode(object);
 @patch
 class Object {
   @patch
+  bool operator==(other) => identical(this, other);
+
+  @patch
   int get hashCode => Primitives.objectHashCode(this);
 
 
@@ -66,6 +69,12 @@ class Object {
   Type get runtimeType => getRuntimeType(this);
 }
 
+@patch
+class Null {
+  @patch
+  int get hashCode => super.hashCode;
+}
+
 // Patch for Function implementation.
 @patch
 class Function {
@@ -207,6 +216,33 @@ class Error {
   StackTrace get stackTrace => Primitives.extractStackTrace(this);
 }
 
+@patch
+class FallThroughError {
+  @patch
+  String toString() => super.toString();
+}
+
+@patch
+class AbstractClassInstantiationError {
+  @patch
+  String toString() => "Cannot instantiate abstract class: '$_className'";
+}
+
+@patch
+class NoSuchMethodError {
+  @patch
+  NoSuchMethodError(Object receiver,
+                    Symbol memberName,
+                    List positionalArguments,
+                    Map<Symbol, dynamic> namedArguments,
+                    [List existingArgumentNames = null])

[Lasse Reichstein Nielsen, 2016/12/08 12:25:32]

This constructor should never have been public. Probably too late to fix now. :(

+      : _receiver = receiver,
+        _memberName = memberName,
+        _arguments = positionalArguments,
+        _namedArguments = namedArguments,
+        _existingArgumentNames = existingArgumentNames;
+}
+
 // Patch for DateTime implementation.
 @patch
 class DateTime {
@@ -461,6 +497,9 @@ class bool {
     throw new UnsupportedError(
         'bool.fromEnvironment can only be used as a const constructor');
   }
+
+  @patch
+  int get hashCode => super.hashCode;
 }
 
 @patch