Make LinkedHashMap also have a factory constructor and be customizable

tests/corelib/map_test.dart

Index: tests/corelib/map_test.dart
diff --git a/tests/corelib/map_test.dart b/tests/corelib/map_test.dart
index c9ba29f56329d5406b11c94a27b1a1c71b5b1919..1fff2f0c322c31cf653e05001f145064c93e5b39 100644
--- a/tests/corelib/map_test.dart
+++ b/tests/corelib/map_test.dart
@@ -33,6 +33,8 @@ void main() {
   testNumericKeys(new HashMap<num, String>(equals: identical));
   testNumericKeys(new LinkedHashMap());
   testNumericKeys(new LinkedHashMap<num, String>());
+  testNumericKeys(new LinkedHashMap(equals: identical));
+  testNumericKeys(new LinkedHashMap<num, String>(equals: identical));
 
   testNaNKeys(new Map());
   testNaNKeys(new Map<num, String>());
@@ -44,10 +46,13 @@ void main() {
   // NaN is not equal to NaN.
 
   testIdentityMap(new HashMap(equals: identical));
+  testIdentityMap(new LinkedHashMap(equals: identical));
 
   testCustomMap(new HashMap(equals: myEquals, hashCode: myHashCode));
+  testCustomMap(new LinkedHashMap(equals: myEquals, hashCode: myHashCode));
 
   testIterationOrder(new LinkedHashMap());
+  testIterationOrder(new LinkedHashMap(equals: identical));
 }