Disallow setting invalid values for registered properties via CSSOM

third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp

Index: third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp
diff --git a/third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp b/third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp
index af1227e168e16b0df4a9f85b3851f6fc0c07827a..fc61883728394dc231b7eda78d72d0e7b16c8fdd 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp
+++ b/third_party/WebKit/Source/core/inspector/InspectorCSSAgent.cpp
@@ -118,8 +118,8 @@ String createShorthandValue(Document* document,
   CSSStyleRule* rule = toCSSStyleRule(styleSheet->item(0));
   CSSStyleDeclaration* style = rule->style();
   DummyExceptionStateForTesting exceptionState;
-  style->setProperty(longhand, newValue, style->getPropertyPriority(longhand),
-                     exceptionState);
+  style->setProperty(nullptr, longhand, newValue,
+                     style->getPropertyPriority(longhand), exceptionState);
   return style->getPropertyValue(shorthand);
 }