Renaming uiManagerWillFlushUIBlocks -> uiManagerWillPerformMounting

Summary:
Because it is not simply flushing, it (in the future) is more complex process. And the names should represent logical meaning of the process, not particular implementation details.
It also nice to have unified terminology across our reactive UI frameworks.

See the next diffs.

Reviewed By: rsnara

Differential Revision: D6436770

fbshipit-source-id: 0a0b686e8ace89e30f6787a37c0a7965c5af757b

Libraries/NativeAnimation/RCTNativeAnimatedModule.m

@@ -34,7 +34,7 @@ - (void)invalidate
 - (dispatch_queue_t)methodQueue
 {
   // This module needs to be on the same queue as the UIManager to avoid
-  // having to lock `_operations` and `_preOperations` since `uiManagerWillFlushUIBlocks`
+  // having to lock `_operations` and `_preOperations` since `uiManagerWillPerformMounting`
   // will be called from that queue.
   return RCTGetUIManagerQueue();
 }
@@ -198,7 +198,7 @@ - (void)addPreOperationBlock:(AnimatedOperation)operation
 
 #pragma mark - RCTUIManagerObserver
 
-- (void)uiManagerWillFlushUIBlocks:(RCTUIManager *)uiManager
+- (void)uiManagerWillPerformMounting:(RCTUIManager *)uiManager
 {
   if (_preOperations.count == 0 && _operations.count == 0) {
     return;

React/Modules/RCTUIManager.m

@@ -1126,7 +1126,7 @@ - (void)_layoutAndMount
     }
   }];
 
-  [_observerCoordinator uiManagerWillFlushUIBlocks:self];
+  [_observerCoordinator uiManagerWillPerformMounting:self];
 
   [self flushUIBlocks];
 }

React/Modules/RCTUIManagerObserverCoordinator.h

@@ -43,7 +43,7 @@
  * Called before flushing UI blocks at the end of a batch.
  * This is called from the UIManager queue. Can be used to add UI operations in that batch.
  */
-- (void)uiManagerWillFlushUIBlocks:(RCTUIManager *)manager;
+- (void)uiManagerWillPerformMounting:(RCTUIManager *)manager;
 
 @end
 

React/Modules/RCTUIManagerObserverCoordinator.mm

@@ -63,13 +63,13 @@ - (void)uiManagerDidPerformLayout:(RCTUIManager *)manager
   }
 }
 
-- (void)uiManagerWillFlushUIBlocks:(RCTUIManager *)manager
+- (void)uiManagerWillPerformMounting:(RCTUIManager *)manager
 {
   std::lock_guard<std::mutex> lock(_mutex);
 
   for (id<RCTUIManagerObserver> observer in _observers) {
-    if ([observer respondsToSelector:@selector(uiManagerWillFlushUIBlocks:)]) {
-      [observer uiManagerWillFlushUIBlocks:manager];
+    if ([observer respondsToSelector:@selector(uiManagerWillPerformMounting:)]) {
+      [observer uiManagerWillPerformMounting:manager];
     }
   }
 }