Editing: queryCommandValue("stylewithcss") should always return an empty string.

third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp

Index: third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp
diff --git a/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp b/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp
index 92361081d6e1325c3822f2ac6e559fe131611154..1d6c3ecd17ef9db3c9b0056c1a5eb4933fde263b 100644
--- a/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp
+++ b/third_party/WebKit/Source/core/editing/commands/EditorCommand.cpp
@@ -2203,6 +2203,13 @@ static String valueNull(LocalFrame&, Event*) {
   return String();
 }
 
+// The command has no value.
+// https://w3c.github.io/editing/execCommand.html#querycommandvalue()
+// > ... or has no value, return the empty string.
+static String valueNo(LocalFrame&, Event*) {
+  return emptyString;
+}
+
 static String valueBackColor(LocalFrame& frame, Event*) {
   return valueStyle(frame, CSSPropertyBackgroundColor);
 }
@@ -2657,7 +2664,7 @@ static const EditorInternalCommand* internalCommand(const String& commandName) {
        enabledInRichlyEditableText, stateStrikethrough, valueNull,
        notTextInsertion, doNotAllowExecutionWhenDisabled},
       {WebEditingCommandType::StyleWithCSS, executeStyleWithCSS, supported,
-       enabled, stateStyleWithCSS, valueNull, notTextInsertion,
+       enabled, stateStyleWithCSS, valueNo, notTextInsertion,
        doNotAllowExecutionWhenDisabled},
       {WebEditingCommandType::Subscript, executeSubscript, supported,
        enabledInRichlyEditableText, stateSubscript, valueNull, notTextInsertion,