[Parser] Consistently use consumeIdentifier() for normal identifiers.

consumeIdentifier() provides the general way in which we consume an
identifier token and fill in an Identifier. Use it consistently in the
parser.

lib/Parse/ParseGeneric.cpp

@@ -297,8 +297,8 @@ ParserStatus Parser::parseGenericWhereClause(
           getLayoutConstraint(Context.getIdentifier(Tok.getText()), Context)
               ->isKnownLayout()) {
         // Parse a layout constraint.
-        auto LayoutName = Context.getIdentifier(Tok.getText());
-        auto LayoutLoc = consumeToken();
+        Identifier LayoutName;
+        auto LayoutLoc = consumeIdentifier(&LayoutName);
         auto LayoutInfo = parseLayoutConstraint(LayoutName);
         if (!LayoutInfo->isKnownLayout()) {
           // There was a bug in the layout constraint.