Use actual CADisplayLink timestamp for VSYNC

Summary:
public

Use the actual timestamp provided through `CADisplayLink` instead of the time
the handler is called.

Reviewed By: jspahrsummers

Differential Revision: D2739121

fb-gh-sync-id: 1da28190bb25351dc3dd94efaff21d49279a570f

React/Base/RCTBatchedBridge.m

@@ -943,7 +943,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
   [self updateJSDisplayLinkState];
 
 
-  RCTProfileImmediateEvent(0, @"JS Thread Tick", 'g');
+  RCTProfileImmediateEvent(0, @"JS Thread Tick", displayLink.timestamp, 'g');
 
   RCT_PROFILE_END_EVENT(0, @"objc_call", nil);
 }

React/Profiler/RCTProfile.h

@@ -124,6 +124,7 @@ RCT_EXTERN void RCTProfileEndAsyncEvent(uint64_t tag,
  */
 RCT_EXTERN void RCTProfileImmediateEvent(uint64_t tag,
                                          NSString *name,
+                                         NSTimeInterval time,
                                          char scope);
 
 /**

React/Profiler/RCTProfile.m

@@ -275,9 +275,9 @@ void RCTProfileUnhookModules(RCTBridge *bridge)
 
 @implementation RCTProfile
 
-+ (void)vsync:(__unused CADisplayLink *)displayLink
++ (void)vsync:(CADisplayLink *)displayLink
 {
-  RCTProfileImmediateEvent(0, @"VSYNC", 'g');
+  RCTProfileImmediateEvent(0, @"VSYNC", displayLink.timestamp, 'g');
 }
 
 @end
@@ -513,6 +513,7 @@ void RCTProfileEndAsyncEvent(
 void RCTProfileImmediateEvent(
   uint64_t tag,
   NSString *name,
+  NSTimeInterval time,
   char scope
 ) {
   CHECK();
@@ -522,7 +523,6 @@ void RCTProfileImmediateEvent(
     return;
   }
 
-  NSTimeInterval time = CACurrentMediaTime();
   NSString *threadName = RCTCurrentThreadName();
 
   dispatch_async(RCTProfileGetQueue(), ^{