Make normalizeEventType public (facebook#45900)

Summary:
Pull Request resolved: facebook#45900

Changelog: [internal]

make `normalizeEventType` public, it looks like a nice util when we want to write code to intercept event, e.g. "scroll" event could be named as "onScroll" or "topScroll", this function contains the source of truth of how RN parses it

Reviewed By: christophpurrer

Differential Revision: D60767388

fbshipit-source-id: b3880fda57e2d92d9d199db5f5d39b8a8435820c

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.cpp

@@ -26,7 +26,7 @@ static bool hasPrefix(const std::string& str, const std::string& prefix) {
  * "top" prefix. E.g. "eventName" becomes "topEventName", "onEventName" also
  * becomes "topEventName".
  */
-static std::string normalizeEventType(std::string type) {
+/* static */ std::string EventEmitter::normalizeEventType(std::string type) {
   auto prefixedType = std::move(type);
   if (facebook::react::hasPrefix(prefixedType, "top")) {
     return prefixedType;

packages/react-native/ReactCommon/react/renderer/core/EventEmitter.h

@@ -33,6 +33,8 @@ class EventEmitter {
  public:
   using Shared = std::shared_ptr<const EventEmitter>;
 
+  static std::string normalizeEventType(std::string type);
+
   static std::mutex& DispatchMutex();
 
   static ValueFactory defaultPayloadFactory();