iOS: RCTImageLoader: use static request counter for request IDs (#42720)

Summary:
Pull Request resolved: #42720

The request ID was used for in-memory request caching purpose only. There wasn't much reason to use the sophisticated monotonic number, so let's just use a static 64-bit unsigned int counter. With the more-or-less unique UUID prefix, this should have an extremely low chance of collision.

Changelog: [Internal]

Reviewed By: philIip, sammy-SC

Differential Revision: D53205641

fbshipit-source-id: e6da12029624058dc877e9cbe2000af4df938870

packages/react-native/Libraries/Image/RCTImageLoader.mm

@@ -44,16 +44,10 @@ static NSInteger RCTImageBytesForImage(UIImage *image)
   return image.images ? image.images.count * singleImageBytes : singleImageBytes;
 }
 
-static uint64_t monotonicTimeGetCurrentNanoseconds(void)
+static uint64_t getNextImageRequestCount(void)
 {
-  static struct mach_timebase_info tb_info = {0};
-  static dispatch_once_t onceToken;
-  dispatch_once(&onceToken, ^{
-    __unused int ret = mach_timebase_info(&tb_info);
-    assert(0 == ret);
-  });
-
-  return (mach_absolute_time() * tb_info.numer) / tb_info.denom;
+  static uint64_t requestCounter = 0;
+  return requestCounter++;
 }
 
 static NSError *addResponseHeadersToError(NSError *originalError, NSHTTPURLResponse *response)
@@ -528,8 +522,7 @@ - (RCTImageURLLoaderRequest *)_loadImageOrDataWithURLRequest:(NSURLRequest *)req
   auto cancelled = std::make_shared<std::atomic<int>>(0);
   __block dispatch_block_t cancelLoad = nil;
   __block NSLock *cancelLoadLock = [NSLock new];
-  NSString *requestId =
-      [NSString stringWithFormat:@"%@-%llu", [[NSUUID UUID] UUIDString], monotonicTimeGetCurrentNanoseconds()];
+  NSString *requestId = [NSString stringWithFormat:@"%@-%llu", [[NSUUID UUID] UUIDString], getNextImageRequestCount()];
 
   void (^completionHandler)(NSError *, id, id, NSURLResponse *) =
       ^(NSError *error, id imageOrData, id imageMetadata, NSURLResponse *response) {