[DevTools] migrate InspectorCSSAgent to new style

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

Index: third_party/WebKit/Source/core/inspector/LayoutEditor.cpp
diff --git a/third_party/WebKit/Source/core/inspector/LayoutEditor.cpp b/third_party/WebKit/Source/core/inspector/LayoutEditor.cpp
index 90566eb71e1521ea88b417a4c2a0821c95c4d815..8b60d1d168d057b5ffbb677e2cf761ec24f05c4b 100644
--- a/third_party/WebKit/Source/core/inspector/LayoutEditor.cpp
+++ b/third_party/WebKit/Source/core/inspector/LayoutEditor.cpp
@@ -417,11 +417,10 @@ std::unique_ptr<protocol::DictionaryValue> LayoutEditor::currentSelectorInfo(
 }
 
 bool LayoutEditor::setCSSPropertyValueInCurrentRule(const String& value) {
-  ErrorString errorString;
-  m_cssAgent->setLayoutEditorValue(&errorString, m_element.get(),
-                                   m_matchedStyles.at(m_currentRuleIndex),
-                                   m_changingProperty, value, false);
-  return errorString.isEmpty();
+  Response response = m_cssAgent->setLayoutEditorValue(
+      m_element.get(), m_matchedStyles.at(m_currentRuleIndex),
+      m_changingProperty, value, false);
+  return response.isSuccess();
 }
 
 void LayoutEditor::evaluateInOverlay(