Implement caretHidden in multiline text input

Summary:
Changelog: [internal]

Add missing implementation of caretHidden to multiline text input. This will work for both React Native Classic and New React Native Renderer.

Reviewed By: shergin

Differential Revision: D26818087

fbshipit-source-id: 3597604a6bd414a4a3b292d809d63a18efa8acb3

Libraries/Text/TextInput/Multiline/RCTUITextView.h

@@ -33,8 +33,6 @@ NS_ASSUME_NONNULL_BEGIN
 // it's declared here only to conform to the interface.
 @property (nonatomic, assign) UITextFieldViewMode clearButtonMode;
 
-// The `caretHidden` property actually is not supported yet;
-// it's declared here only to conform to the interface.
 @property (nonatomic, assign) BOOL caretHidden;
 
 @property (nonatomic, strong, nullable) NSString *inputAccessoryViewID;

Libraries/Text/TextInput/Multiline/RCTUITextView.m

@@ -165,8 +165,6 @@ static UIColor *defaultPlaceholderColor()
   [self textDidChange];
 }
 
-#pragma mark - Overrides
-
 - (void)setSelectedTextRange:(UITextRange *)selectedTextRange notifyDelegate:(BOOL)notifyDelegate
 {
   if (!notifyDelegate) {
@@ -298,6 +296,17 @@ static UIColor *defaultPlaceholderColor()
   return textAttributes;
 }
 
+#pragma mark - Caret Manipulation
+
+- (CGRect)caretRectForPosition:(UITextPosition *)position
+{
+  if (_caretHidden) {
+    return CGRectZero;
+  }
+
+  return [super caretRectForPosition:position];
+}
+
 #pragma mark - Utility Methods
 
 - (void)copyTextAttributesFrom:(NSAttributedString *)sourceString