Add property to CssStyleDeclaration to detect if a CSS value is available.

sdk/lib/_blink/dartium/_blink_dartium.dart

Index: sdk/lib/_blink/dartium/_blink_dartium.dart
diff --git a/sdk/lib/_blink/dartium/_blink_dartium.dart b/sdk/lib/_blink/dartium/_blink_dartium.dart
index 354c8c69a51d1f307c2a45c6233da2a129fcadd6..46c7d12a122f24c159f78ae9a6ed3952cd5818a4 100644
--- a/sdk/lib/_blink/dartium/_blink_dartium.dart
+++ b/sdk/lib/_blink/dartium/_blink_dartium.dart
@@ -711,6 +711,8 @@ class BlinkCSSStyleDeclaration {
 
   static $parentRule_Getter(mthis) native "CSSStyleDeclaration_parentRule_Getter";
 
+  static $__propertyQuery___Callback(mthis, name) native "CSSStyleDeclaration___propertyQuery___Callback_RESOLVER_STRING_1_DOMString";
+
   static $__setter___Callback(mthis, propertyName, propertyValue) native "CSSStyleDeclaration___setter___Callback";
 
   static $getPropertyPriority_Callback(mthis, propertyName) native "CSSStyleDeclaration_getPropertyPriority_Callback_RESOLVER_STRING_1_DOMString";
@@ -9509,4 +9511,4 @@ class Blink_DOMStringMap {
   static remove(_DOMStringMap, key) native "DOMStringMap_remove_Callback";
 
   static get_keys(_DOMStringMap) native "DOMStringMap_getKeys_Callback";
-}
+}