Remove factory body in *.fromEnvironment, and implement this same behavior

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 eff2cd712a2b2fd368d02e3b1717c4f99af4fe79..610c1caaa35fe2d7f2b8b9276cc6a547405ad974 100644
--- a/sdk/lib/_internal/js_runtime/lib/core_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/core_patch.dart
@@ -168,12 +168,6 @@ class int {
   static int parse(String source, {int radix, int onError(String source)}) {
     return Primitives.parseInt(source, radix, onError);
   }
-
-  @patch
-  factory int.fromEnvironment(String name, {int defaultValue}) {
-    throw new UnsupportedError(
-        'int.fromEnvironment can only be used as a const constructor');
-  }
 }
 
 @patch
@@ -414,12 +408,6 @@ class String {
     return Primitives.stringFromCharCode(charCode);
   }
 
-  @patch
-  factory String.fromEnvironment(String name, {String defaultValue}) {
-    throw new UnsupportedError(
-        'String.fromEnvironment can only be used as a const constructor');
-  }
-
   static String _stringFromJSArray(List list, int start, int endOrNull) {
     int len = list.length;
     int end = RangeError.checkValidRange(start, endOrNull, len);
@@ -466,12 +454,6 @@ class String {
 @patch
 class bool {
   @patch
-  factory bool.fromEnvironment(String name, {bool defaultValue: false}) {
-    throw new UnsupportedError(
-        'bool.fromEnvironment can only be used as a const constructor');
-  }
-
-  @patch
   int get hashCode => super.hashCode;
 }