Add an event start timestamp field into RawEvent

Summary:
# Changelog:

[Internal] - 

This adds an (optional) event start time field into RawEvent, so that it can be threaded by the platform-specific code to tell where is the earliest point of the event start (depending on the platform).

For example, on Android platform it can be the point of time when the original MotionEvent was received.

Differential Revision: D64175467

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

@@ -37,8 +37,8 @@ void EventDispatcher::dispatchEvent(RawEvent&& rawEvent) const {
 
   auto eventLogger = eventLogger_.lock();
   if (eventLogger != nullptr) {
-    rawEvent.loggingTag =
-        eventLogger->onEventStart(rawEvent.type, rawEvent.eventTarget);
+    rawEvent.loggingTag = eventLogger->onEventStart(
+        rawEvent.type, rawEvent.eventTarget, rawEvent.eventStartTimeStamp);
   }
   eventQueue_.enqueueEvent(std::move(rawEvent));
 }

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

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <react/renderer/core/EventTarget.h>
+#include <react/timing/primitives.h>
 #include <string_view>
 
 namespace facebook::react {
@@ -30,7 +31,9 @@ class EventLogger {
    */
   virtual EventTag onEventStart(
       std::string_view name,
-      SharedEventTarget target) = 0;
+      SharedEventTarget target,
+      DOMHighResTimeStamp eventStartTimeStamp =
+          DOM_HIGH_RES_TIME_STAMP_UNSET) = 0;
 
   /*
    * Called when event starts getting dispatched (processed by the handlers, if

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

@@ -13,6 +13,7 @@
 #include <react/renderer/core/EventLogger.h>
 #include <react/renderer/core/EventPayload.h>
 #include <react/renderer/core/EventTarget.h>
+#include <react/timing/primitives.h>
 
 namespace facebook::react {
 
@@ -69,6 +70,11 @@ struct RawEvent {
   SharedEventTarget eventTarget;
   Category category;
   EventTag loggingTag{0};
+
+  // The client may specify a platform-specific timestamp for the event start
+  // time, for example when MotionEvent was triggered on the Android native
+  // side.
+  DOMHighResTimeStamp eventStartTimeStamp{DOM_HIGH_RES_TIME_STAMP_UNSET};
 };
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/observers/events/EventPerformanceLogger.cpp

@@ -103,7 +103,8 @@ EventPerformanceLogger::EventPerformanceLogger(
 
 EventTag EventPerformanceLogger::onEventStart(
     std::string_view name,
-    SharedEventTarget target) {
+    SharedEventTarget target,
+    DOMHighResTimeStamp eventStartTimeStamp) {
   auto performanceEntryReporter = performanceEntryReporter_.lock();
   if (performanceEntryReporter == nullptr) {
     return EMPTY_EVENT_TAG;
@@ -119,7 +120,11 @@ EventTag EventPerformanceLogger::onEventStart(
 
   auto eventTag = createEventTag();
 
-  auto timeStamp = performanceEntryReporter->getCurrentTimeStamp();
+  // The event start timestamp may be provided by the caller in order to
+  // specify the platform specific event start time.
+  auto timeStamp = eventStartTimeStamp == DOM_HIGH_RES_TIME_STAMP_UNSET
+      ? performanceEntryReporter->getCurrentTimeStamp()
+      : eventStartTimeStamp;
   {
     std::lock_guard lock(eventsInFlightMutex_);
     eventsInFlight_.emplace(

packages/react-native/ReactCommon/react/renderer/observers/events/EventPerformanceLogger.h

@@ -27,8 +27,11 @@ class EventPerformanceLogger : public EventLogger,
 
 #pragma mark - EventLogger
 
-  EventTag onEventStart(std::string_view name, SharedEventTarget target)
-      override;
+  EventTag onEventStart(
+      std::string_view name,
+      SharedEventTarget target,
+      DOMHighResTimeStamp eventStartTimeStamp =
+          DOM_HIGH_RES_TIME_STAMP_UNSET) override;
   void onEventProcessingStart(EventTag tag) override;
   void onEventProcessingEnd(EventTag tag) override;
 

packages/react-native/ReactCommon/react/timing/primitives.h

@@ -17,6 +17,8 @@ namespace facebook::react {
 // not necessary in React Native.
 using DOMHighResTimeStamp = double;
 
+constexpr DOMHighResTimeStamp DOM_HIGH_RES_TIME_STAMP_UNSET = -1.0;
+
 inline DOMHighResTimeStamp chronoToDOMHighResTimeStamp(
     std::chrono::steady_clock::duration duration) {
   return static_cast<std::chrono::duration<double, std::milli>>(duration)