Typing fixes to eliminate casts/dcalls

tool/input_sdk/patch/collection_patch.dart

Index: tool/input_sdk/patch/collection_patch.dart
diff --git a/tool/input_sdk/patch/collection_patch.dart b/tool/input_sdk/patch/collection_patch.dart
index 184e8ce0406dc712fdce761171c144e1d95e7270..c06f55287fa27ca6a9a528bb78ee00ad1017680a 100644
--- a/tool/input_sdk/patch/collection_patch.dart
+++ b/tool/input_sdk/patch/collection_patch.dart
@@ -12,7 +12,7 @@ class HashMap<K, V> {
   @patch
   factory HashMap({ bool equals(K key1, K key2),
                     int hashCode(K key),
-                    bool isValidKey(potentialKey) }) {
+                    bool isValidKey(Object potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -384,8 +384,9 @@ class _IdentityHashMap<K, V> extends _HashMap<K, V> {
 class _CustomHashMap<K, V> extends _HashMap<K, V> {
   final _Equality<K> _equals;
   final _Hasher<K> _hashCode;
-  final _Predicate _validKey;
-  _CustomHashMap(this._equals, this._hashCode, bool validKey(potentialKey))
+  final _Predicate<Object> _validKey;
+  _CustomHashMap(this._equals, this._hashCode,
+                 bool validKey(Object potentialKey))
       : _validKey = (validKey != null) ? validKey : ((v) => v is K);
 
   V operator[](Object key) {
@@ -487,7 +488,7 @@ class LinkedHashMap<K, V> {
   @patch
   factory LinkedHashMap({ bool equals(K key1, K key2),
                           int hashCode(K key),
-                          bool isValidKey(potentialKey) }) {
+                          bool isValidKey(Object potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -859,9 +860,9 @@ class _LinkedIdentityHashMap<K, V> extends _LinkedHashMap<K, V> {
 class _LinkedCustomHashMap<K, V> extends _LinkedHashMap<K, V> {
   final _Equality<K> _equals;
   final _Hasher<K> _hashCode;
-  final _Predicate _validKey;
+  final _Predicate<Object> _validKey;
   _LinkedCustomHashMap(this._equals, this._hashCode,
-                       bool validKey(potentialKey))
+                       bool validKey(Object potentialKey))
       : _validKey = (validKey != null) ? validKey : ((v) => v is K);
 
   V operator[](Object key) {
@@ -971,7 +972,7 @@ class HashSet<E> {
   @patch
   factory HashSet({ bool equals(E e1, E e2),
                     int hashCode(E e),
-                    bool isValidKey(potentialKey) }) {
+                    bool isValidKey(Object potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -1300,8 +1301,9 @@ class _IdentityHashSet<E> extends _HashSet<E> {
 class _CustomHashSet<E> extends _HashSet<E> {
   _Equality<E> _equality;
   _Hasher<E> _hasher;
-  _Predicate _validKey;
-  _CustomHashSet(this._equality, this._hasher, bool validKey(potentialKey))
+  _Predicate<Object> _validKey;
+  _CustomHashSet(this._equality, this._hasher,
+                 bool validKey(Object potentialKey))
       : _validKey = (validKey != null) ? validKey : ((x) => x is E);
 
   Set<E> _newSet() => new _CustomHashSet<E>(_equality, _hasher, _validKey);
@@ -1376,7 +1378,7 @@ class LinkedHashSet<E> {
   @patch
   factory LinkedHashSet({ bool equals(E e1, E e2),
                           int hashCode(E e),
-                          bool isValidKey(potentialKey) }) {
+                          bool isValidKey(Object potentialKey) }) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
@@ -1742,9 +1744,9 @@ class _LinkedIdentityHashSet<E> extends _LinkedHashSet<E> {
 class _LinkedCustomHashSet<E> extends _LinkedHashSet<E> {
   _Equality<E> _equality;
   _Hasher<E> _hasher;
-  _Predicate _validKey;
+  _Predicate<Object> _validKey;
   _LinkedCustomHashSet(this._equality, this._hasher,
-                       bool validKey(potentialKey))
+                       bool validKey(Object potentialKey))
       : _validKey = (validKey != null) ? validKey : ((x) => x is E);
 
   Set<E> _newSet() =>