clang-format: [JS] respect clang-format off when requoting strings.

[djasper]

Looks good.

lib/Format/Format.cpp

void requoteJSStringLiteral(SmallVectorImpl<AnnotatedLine *> &Lines,
                               tooling::Replacements &Result) {
     for (AnnotatedLine *Line : Lines) {
       requoteJSStringLiteral(Line->Children, Result);
       if (!Line->Affected)
         continue;
       for (FormatToken *FormatTok = Line->First; FormatTok;
            FormatTok = FormatTok->Next) {
         StringRef Input = FormatTok->TokenText;
-        if (!FormatTok->isStringLiteral() ||
+        if (FormatTok->Finalized || !FormatTok->isStringLiteral() ||
             // NB: testing for not starting with a double quote to avoid
             // breaking
             // `template strings`.
             (Style.JavaScriptQuotes == FormatStyle::JSQS_Single &&
              !Input.startswith("\"")) ||
             (Style.JavaScriptQuotes == FormatStyle::JSQS_Double &&
              !Input.startswith("\'")))
           continue;

unittests/Format/FormatTestJS.cpp

verifyFormat(
       // Code below is 15 chars wide, doesn't fit into the line with the
       // \ escape added.
       "var x = \"foo'\";", getGoogleJSStyleWithColumns(15));
   // Removes no-longer needed \ escape from ".
   verifyFormat("var x = 'fo\"o';", "var x = \"fo\\\"o\";");
   // Code below fits into 15 chars *after* removing the \ escape.
   verifyFormat("var x = 'fo\"o';", "var x = \"fo\\\"o\";",
                getGoogleJSStyleWithColumns(15));
+  verifyFormat("// clang-format off\n"
+               "let x = \"double\";\n"
+               "// clang-format on\n"
+               "let x = 'single';\n",
+               "// clang-format off\n"
+               "let x = \"double\";\n"
+               "// clang-format on\n"
+               "let x = \"single\";\n");
 }
 
 TEST_F(FormatTestJS, RequoteStringsDouble) {
   FormatStyle DoubleQuotes = getGoogleStyle(FormatStyle::LK_JavaScript);
   DoubleQuotes.JavaScriptQuotes = FormatStyle::JSQS_Double;
   verifyFormat("var x = \"foo\";", DoubleQuotes);
   verifyFormat("var x = \"foo\";", "var x = 'foo';", DoubleQuotes);
   verifyFormat("var x = \"fo'o\";", "var x = 'fo\\'o';", DoubleQuotes);