Add an event start timestamp field into RawEvent

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/core/tests/EventQueueProcessorTest.cpp

@@ -21,8 +21,10 @@
 namespace facebook::react {
 
 class MockEventLogger : public EventLogger {
-  EventTag onEventStart(std::string_view /*name*/, SharedEventTarget /*target*/)
-      override {
+  EventTag onEventStart(
+      std::string_view /*name*/,
+      SharedEventTarget /*target*/,
+      DOMHighResTimeStamp /*eventStartTimeStamp*/) override {
     return EMPTY_EVENT_TAG;
   }
   void onEventProcessingStart(EventTag /*tag*/) override {}

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)