Revert "[vm,dart2wasm] Move hash factory code to enable sharing of patch files"

This reverts commit 04372ad.

Reason for revert: Flutter PR not rolled into g3 yet.

Original change's description:
> [vm,dart2wasm] Move hash factory code to enable sharing of patch files
>
> By moving the hash map/set factories into their own file, the
> collection_patch and compact_hash patch files can be shared between the
> VM and dart2wasm.
>
> This builds on the preparations from the creation of the file in
> https://dart-review.googlesource.com/c/sdk/+/229905 and listing it in
> the Flutter file lists in flutter/engine#31133.
>
> Change-Id: Ia8f07229af056e59b119008714deecc0c96dd742
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/231947
> Reviewed-by: Daco Harkes <dacoharkes@google.com>
> Commit-Queue: Aske Simon Christensen <askesc@google.com>

TBR=askesc@google.com,dacoharkes@google.com

Change-Id: I6342ef0250cc24b36c4c32e86a4769dbaeffafa4
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/232400
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Aske Simon Christensen <askesc@google.com>

Author: askeksa

sdk/lib/_internal/vm/lib/collection_patch.dart

@@ -849,3 +849,72 @@ class _HashSetIterator<E> implements Iterator<E> {
 
   E get current => _current as E;
 }
+
+/**
+ * A hash-based map that iterates keys and values in key insertion order.
+ * This is never actually instantiated any more - the constructor always
+ * returns an instance of _CompactLinkedHashMap or _InternalLinkedHashMap,
+ * which despite the names do not use links (but are insertion-ordered as if
+ * they did).
+ */
+@patch
+class LinkedHashMap<K, V> {
+  @patch
+  factory LinkedHashMap(
+      {bool equals(K key1, K key2)?,
+      int hashCode(K key)?,
+      bool isValidKey(potentialKey)?}) {
+    if (isValidKey == null) {
+      if (hashCode == null) {
+        if (equals == null) {
+          return new _InternalLinkedHashMap<K, V>();
+        }
+        hashCode = _defaultHashCode;
+      } else {
+        if (identical(identityHashCode, hashCode) &&
+            identical(identical, equals)) {
+          return new _CompactLinkedIdentityHashMap<K, V>();
+        }
+        equals ??= _defaultEquals;
+      }
+    } else {
+      hashCode ??= _defaultHashCode;
+      equals ??= _defaultEquals;
+    }
+    return new _CompactLinkedCustomHashMap<K, V>(equals, hashCode, isValidKey);
+  }
+
+  @patch
+  factory LinkedHashMap.identity() => new _CompactLinkedIdentityHashMap<K, V>();
+}
+
+@patch
+class LinkedHashSet<E> {
+  @patch
+  factory LinkedHashSet(
+      {bool equals(E e1, E e2)?,
+      int hashCode(E e)?,
+      bool isValidKey(potentialKey)?}) {
+    if (isValidKey == null) {
+      if (hashCode == null) {
+        if (equals == null) {
+          return new _CompactLinkedHashSet<E>();
+        }
+        hashCode = _defaultHashCode;
+      } else {
+        if (identical(identityHashCode, hashCode) &&
+            identical(identical, equals)) {
+          return new _CompactLinkedIdentityHashSet<E>();
+        }
+        equals ??= _defaultEquals;
+      }
+    } else {
+      hashCode ??= _defaultHashCode;
+      equals ??= _defaultEquals;
+    }
+    return new _CompactLinkedCustomHashSet<E>(equals, hashCode, isValidKey);
+  }
+
+  @patch
+  factory LinkedHashSet.identity() => new _CompactLinkedIdentityHashSet<E>();
+}

sdk/lib/_internal/vm/lib/hash_factories.dart

@@ -2,67 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// The [LinkedHashMap] and [LinkedHashSet] factory constructors return different
-// internal implementations depending on the supplied callback functions.
-
-@patch
-class LinkedHashMap<K, V> {
-  @patch
-  factory LinkedHashMap(
-      {bool equals(K key1, K key2)?,
-      int hashCode(K key)?,
-      bool isValidKey(potentialKey)?}) {
-    if (isValidKey == null) {
-      if (hashCode == null) {
-        if (equals == null) {
-          return new _InternalLinkedHashMap<K, V>();
-        }
-        hashCode = _defaultHashCode;
-      } else {
-        if (identical(identityHashCode, hashCode) &&
-            identical(identical, equals)) {
-          return new _CompactLinkedIdentityHashMap<K, V>();
-        }
-        equals ??= _defaultEquals;
-      }
-    } else {
-      hashCode ??= _defaultHashCode;
-      equals ??= _defaultEquals;
-    }
-    return new _CompactLinkedCustomHashMap<K, V>(equals, hashCode, isValidKey);
-  }
-
-  @patch
-  factory LinkedHashMap.identity() => new _CompactLinkedIdentityHashMap<K, V>();
-}
-
-@patch
-class LinkedHashSet<E> {
-  @patch
-  factory LinkedHashSet(
-      {bool equals(E e1, E e2)?,
-      int hashCode(E e)?,
-      bool isValidKey(potentialKey)?}) {
-    if (isValidKey == null) {
-      if (hashCode == null) {
-        if (equals == null) {
-          return new _CompactLinkedHashSet<E>();
-        }
-        hashCode = _defaultHashCode;
-      } else {
-        if (identical(identityHashCode, hashCode) &&
-            identical(identical, equals)) {
-          return new _CompactLinkedIdentityHashSet<E>();
-        }
-        equals ??= _defaultEquals;
-      }
-    } else {
-      hashCode ??= _defaultHashCode;
-      equals ??= _defaultEquals;
-    }
-    return new _CompactLinkedCustomHashSet<E>(equals, hashCode, isValidKey);
-  }
-
-  @patch
-  factory LinkedHashSet.identity() => new _CompactLinkedIdentityHashSet<E>();
-}
+// This is a placeholder file which will shortly contain the LinkedhashMap and
+// LinkedHashSet patches from collection_patch.dart. The change is done in two
+// steps to ease rolling it into Flutter.