Add missing default labels to CSS parser switch statements

Summary:
Add missing `default` labels to `switch` statements in CSS parser headers
(`CSSTokenizer.h`, `CSSSyntaxParser.h`, `CSSKeyword.h`) and move away from switch/case in `CSSColor.h` to fix `-Werror` build failures when
fbobjc targets import CSS headers.

Changelog: [Internal]

Differential Revision: D94074704

Author: NickGerleman

packages/react-native/ReactCommon/react/renderer/css/CSSColor.h

@@ -38,14 +38,13 @@ template <>
 struct CSSDataTypeParser<CSSColor> {
   static constexpr auto consumePreservedToken(const CSSPreservedToken &token) -> std::optional<CSSColor>
   {
-    switch (token.type()) {
-      case CSSTokenType::Ident:
-        return parseCSSNamedColor<CSSColor>(token.stringValue());
-      case CSSTokenType::Hash:
-        return parseCSSHexColor<CSSColor>(token.stringValue());
-      default:
-        return {};
+    if (token.type() == CSSTokenType::Ident) {
+      return parseCSSNamedColor<CSSColor>(token.stringValue());
+    } else if (token.type() == CSSTokenType::Hash) {
+      return parseCSSHexColor<CSSColor>(token.stringValue());
     }
+
+    return {};
   }
 
   static constexpr auto consumeFunctionBlock(const CSSFunctionBlock &func, CSSSyntaxParser &parser)

packages/react-native/ReactCommon/react/renderer/css/CSSKeyword.h

@@ -346,9 +346,9 @@ constexpr std::optional<KeywordT> parseCSSKeyword(std::string_view ident)
     CSS_HANDLE_KEYWORD(Visible)
     CSS_HANDLE_KEYWORD(Wrap)
     CSS_HANDLE_KEYWORD(WrapReverse)
+    default:
+      return std::nullopt;
   }
-
-  return std::nullopt;
 }
 
 template <CSSKeywordSet KeywordT>

packages/react-native/ReactCommon/react/renderer/css/CSSSyntaxParser.h

@@ -226,9 +226,9 @@ class CSSSyntaxParser {
         return hasWhiteSpace;
       case CSSDelimiter::None:
         return true;
+      default:
+        return false;
     }
-
-    return false;
   }
 
  private:

packages/react-native/ReactCommon/react/renderer/css/CSSTokenizer.h

@@ -67,6 +67,8 @@ class CSSTokenizer {
         } else {
           return consumeDelim();
         }
+      default:
+        break;
     }
 
     if (isDigit(nextChar)) {