[clang-query] Use StringRef::ltrim (NFC)

Author: kazutakahirata

clang-tools-extra/clang-query/QueryParser.cpp

@@ -28,10 +28,8 @@ namespace query {
 // is found before End, return StringRef().  Begin is adjusted to exclude the
 // lexed region.
 StringRef QueryParser::lexWord() {
-  Line = Line.drop_while([](char c) {
-    // Don't trim newlines.
-    return StringRef(" \t\v\f\r").contains(c);
-  });
+  // Don't trim newlines.
+  Line = Line.ltrim(" \t\v\f\r");
 
   if (Line.empty())
     // Even though the Line is empty, it contains a pointer and
@@ -152,8 +150,7 @@ QueryRef QueryParser::parseSetTraversalKind(TraversalKind QuerySession::*Var) {
 
 QueryRef QueryParser::endQuery(QueryRef Q) {
   StringRef Extra = Line;
-  StringRef ExtraTrimmed = Extra.drop_while(
-      [](char c) { return StringRef(" \t\v\f\r").contains(c); });
+  StringRef ExtraTrimmed = Extra.ltrim(" \t\v\f\r");
 
   if ((!ExtraTrimmed.empty() && ExtraTrimmed[0] == '\n') ||
       (ExtraTrimmed.size() >= 2 && ExtraTrimmed[0] == '\r' &&