Revert trial commit of "CssStyleDeclaration performance work"

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 69df1e476921d45626d305f57592e653332ac93d..c8ffdd6d5dad4a1bf436fc78e8c6b3444a2ab8d9 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -4284,25 +4284,14 @@ class CssRule extends NativeFieldWrapperClass2 {
 
   @DomName('CSSStyleDeclaration.setProperty')
   void setProperty(String propertyName, String value, [String priority]) {
-    return _setPropertyHelper(_browserPropertyName(propertyName),
-      value, priority);
-  }
-
-  String _browserPropertyName(String propertyName) {
-    String name = _readCache(propertyName);
-    if (name is String) return name;
     if (_supportsProperty(_camelCase(propertyName))) {
-      name = propertyName;
+      return _setPropertyHelper(propertyName, value, priority);
     } else {
-      name = Device.cssPrefix + propertyName;
+      return _setPropertyHelper(Device.cssPrefix + propertyName, value,
+          priority);
     }
-    _writeCache(propertyName, name);
-    return name;
   }
 
-  static String _readCache(String key) => null;
-  static void _writeCache(String key, value) {}
-
   static String _camelCase(String hyphenated) {
     // The "ms" prefix is always lowercased.
     return hyphenated.replaceFirst(new RegExp('^-ms-'), 'ms-').replaceAllMapped(