Removing reactBridgeDidFinishTransaction from RCTScrollView

Summary:
We are removing `reactBridgeDidFinishTransaction`.
Why?
 * It is a performance drain. Supporting this requires dispatching main-thread block on every single transaction complete;
 * It has "too broad" non-conceptual semantic which encouraged using this as a "band-aid solution" for poorly designed components;
 * It is conceptually incompatible with new approaches that we are trying to implement to optimize the render layer;
 * It was deprecated for very long time.

This diff removes `reactBridgeDidFinishTransaction` from RCTScrollView component. As I mentioned, because of the semantic of `reactBridgeDidFinishTransaction` is extremely broad, it's hard to capture what exact case it should handle. Based on comments and existing logic, it seems it tight to `contentSize` property and the size of RCTScrollContentView.

Reviewed By: rsnara

Differential Revision: D6538419

fbshipit-source-id: ccc6f5fea327471f10f1738d3da5214c0d362953

React/Views/RCTScrollContentView.h

@@ -0,0 +1,16 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <UIKit/UIKit.h>
+
+#import <React/RCTView.h>
+
+@interface RCTScrollContentView : RCTView
+
+@end

React/Views/RCTScrollContentView.m

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "RCTScrollContentView.h"
+
+#import <React/RCTAssert.h>
+#import <React/UIView+React.h>
+
+#import "RCTScrollView.h"
+
+@implementation RCTScrollContentView
+
+- (void)reactSetFrame:(CGRect)frame
+{
+  [super reactSetFrame:frame];
+
+  RCTScrollView *scrollView = (RCTScrollView *)self.superview.superview;
+
+  if (!scrollView) {
+    return;
+  }
+
+  RCTAssert([scrollView isKindOfClass:[RCTScrollView class]],
+            @"Unexpected view hierarchy of RCTScrollView component.");
+
+  [scrollView updateContentOffsetIfNeeded];
+}
+
+@end

React/Views/RCTScrollContentViewManager.m

@@ -10,11 +10,17 @@
 #import "RCTScrollContentViewManager.h"
 
 #import "RCTScrollContentShadowView.h"
+#import "RCTScrollContentView.h"
 
 @implementation RCTScrollContentViewManager
 
 RCT_EXPORT_MODULE()
 
+- (RCTScrollContentView *)view
+{
+  return [RCTScrollContentView new];
+}
+
 - (RCTShadowView *)shadowView
 {
   return [RCTScrollContentShadowView new];

React/Views/RCTScrollView.h

@@ -59,6 +59,12 @@
 
 @end
 
+@interface RCTScrollView (Internal)
+
+- (void)updateContentOffsetIfNeeded;
+
+@end
+
 @interface RCTEventDispatcher (RCTScrollView)
 
 /**

React/Views/RCTScrollView.m

@@ -466,6 +466,13 @@ - (void)didUpdateReactSubviews
   // Do nothing, as subviews are managed by `insertReactSubview:atIndex:`
 }
 
+- (void)didSetProps:(NSArray<NSString *> *)changedProps
+{
+  if ([changedProps containsObject:@"contentSize"]) {
+    [self updateContentOffsetIfNeeded];
+  }
+}
+
 - (BOOL)centerContent
 {
   return _scrollView.centerContent;
@@ -882,7 +889,7 @@ - (CGSize)contentSize
   return _contentView.frame.size;
 }
 
-- (void)reactBridgeDidFinishTransaction
+- (void)updateContentOffsetIfNeeded
 {
   CGSize contentSize = self.contentSize;
   if (!CGSizeEqualToSize(_scrollView.contentSize, contentSize)) {