RCTTextInput: Fixed problem with accessory view & 3rd party libs

Summary:
Now RCTTextInput relies on ivar to detect should it reconstruct inputAccessoryView or not.
Previously we checked `inputAccessoryView` directly which breaks some 3rd party libs.

See https://github.com/facebook/react-native/issues/16071 for more details.
cc douglasjunior

Reviewed By: javache

Differential Revision: D5994798

fbshipit-source-id: c086efdd24f5528393a4c734ff7c984e0ed740d1

Libraries/Text/RCTTextInput.m

@@ -21,6 +21,7 @@
 
 @implementation RCTTextInput {
   CGSize _previousContentSize;
+  BOOL _hasInputAccesoryView;
 }
 
 - (instancetype)initWithBridge:(RCTBridge *)bridge
@@ -304,12 +305,12 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithFrame:(CGRect)frame)
     ) &&
     textInputView.returnKeyType == UIReturnKeyDone;
 
-  BOOL hasInputAccesoryView = textInputView.inputAccessoryView != nil;
-
-  if (hasInputAccesoryView == shouldHaveInputAccesoryView) {
+  if (_hasInputAccesoryView == shouldHaveInputAccesoryView) {
     return;
   }
 
+  _hasInputAccesoryView = shouldHaveInputAccesoryView;
+
   if (shouldHaveInputAccesoryView) {
     UIToolbar *toolbarView = [[UIToolbar alloc] init];
     [toolbarView sizeToFit];