[pop] remove unecessary initial workaround

Summary:

Original benchmarking improperly accounted for external factors. Manually performing the callback is only marginally faster.

FBKVOController/FBKVOController.m

@@ -78,18 +78,6 @@ static NSUInteger enumerate_flags(NSUInteger *ptrFlags)
   return s;
 }
 
-static NSDictionary *change_dictionary_init(id object, NSUInteger options, NSString *keyPath)
-{
-  NSDictionary *dict;
-  if (0 == (NSKeyValueObservingOptionNew & options)) {
-    dict = @{NSKeyValueChangeKindKey : @(NSKeyValueChangeSetting)};
-  } else {
-    id value = [object valueForKeyPath:keyPath];
-    dict = @{NSKeyValueChangeKindKey : @(NSKeyValueChangeSetting), NSKeyValueChangeNewKey : value ?: [NSNull null]};
-  }
-  return dict;
-}
-
 #pragma mark _FBKVOInfo -
 
 /**
@@ -278,16 +266,8 @@ - (void)observe:(id)object info:(_FBKVOInfo *)info
   [_infos addObject:info];
   OSSpinLockUnlock(&_lock);
 
-  // remove costly initial
-  NSUInteger options = info->_options & ~NSKeyValueObservingOptionInitial;
-
   // add observer
-  [object addObserver:self forKeyPath:info->_keyPath options:options context:(void *)info];
-
-  // manually perform initial callback if necessary
-  if (0 != (NSKeyValueObservingOptionInitial & info->_options)) {
-    [self observeValueForKeyPath:info->_keyPath ofObject:object change:change_dictionary_init(object, info->_options, info->_keyPath) context:(void *)info];
-  }
+  [object addObserver:self forKeyPath:info->_keyPath options:info->_options context:(void *)info];
 }
 
 - (void)unobserve:(id)object info:(_FBKVOInfo *)info

README.md

@@ -8,7 +8,6 @@ Key-value observing is a particularly useful technique for communicating between
 - Notification using blocks, custom actions, or NSKeyValueObserving callback.
 - No exceptions on observer removal.
 - Implicit observer removal on controller dealloc.
-- Improved performance when using NSKeyValueObservingInitial.
 - Thread-safety with special guards against observer resurrection – [rdar://15985376](http://openradar.appspot.com/radar?id=5305010728468480).
 
 For more information on KVO, see Apple's [Introduction to Key-Value Observing](https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/KeyValueObserving/KeyValueObserving.html).