Restore VSYNC markers on RCTProfile

Summary: public

The VSYNC markers got lost at some point when refactoring RCTBatchedBridge, restore it, but keep it in RCTProfile.

Reviewed By: jspahrsummers

Differential Revision: D2685805

fb-gh-sync-id: 1acad330de7baf004a83b41f90ba4b6532605de6

React/Profiler/RCTProfile.m

@@ -46,6 +46,7 @@ static NSDictionary *RCTProfileInfo;
 static NSMutableDictionary *RCTProfileOngoingEvents;
 static NSTimeInterval RCTProfileStartTime;
 static NSUInteger RCTProfileEventID = 0;
+static CADisplayLink *RCTProfileDisplayLink;
 
 #pragma mark - Macros
 
@@ -266,6 +267,19 @@ void RCTProfileUnhookModules(RCTBridge *bridge)
   dispatch_group_leave(RCTProfileGetUnhookGroup());
 }
 
+#pragma mark - Private ObjC class only used for the vSYNC CADisplayLink target
+
+@interface RCTProfile : NSObject
+@end
+
+@implementation RCTProfile
+
++ (void)vsync:(__unused CADisplayLink *)displayLink
+{
+  RCTProfileImmediateEvent(0, @"VSYNC", 'g');
+}
+
+@end
 
 #pragma mark - Public Functions
 
@@ -312,6 +326,11 @@ void RCTProfileInit(RCTBridge *bridge)
 
   RCTProfileHookModules(bridge);
 
+  RCTProfileDisplayLink = [CADisplayLink displayLinkWithTarget:[RCTProfile class]
+                                                      selector:@selector(vsync:)];
+  [RCTProfileDisplayLink addToRunLoop:[NSRunLoop mainRunLoop]
+                              forMode:NSRunLoopCommonModes];
+
   [[NSNotificationCenter defaultCenter] postNotificationName:RCTProfileDidStartProfiling
                                                       object:nil];
 }
@@ -329,6 +348,9 @@ void RCTProfileEnd(RCTBridge *bridge, void (^callback)(NSString *))
   [[NSNotificationCenter defaultCenter] postNotificationName:RCTProfileDidEndProfiling
                                                       object:nil];
 
+  [RCTProfileDisplayLink invalidate];
+  RCTProfileDisplayLink = nil;
+
   RCTProfileUnhookModules(bridge);
 
   if (callbacks != NULL) {