multiline textinput view not wrapping in multiline on ios

Summary:
It's because the view doesn't update itself after setText.
Closes https://github.com/facebook/react-native/pull/5247

Reviewed By: svcscm

Differential Revision: D2819520

Pulled By: nicklockwood

fb-gh-sync-id: 06f5342d94f242fc63f862dac738da9b96842183

Libraries/Text/RCTTextView.m

@@ -382,6 +382,8 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithCoder:(NSCoder *)aDecoder)
     }
 
     [self _setPlaceholderVisibility];
+    [self updateContentSize]; //keep the text wrapping when the length of
+    //the textline has been extended longer than the length of textinputView
   } else if (eventLag > RCTTextUpdateLagWarningThreshold) {
     RCTLogWarn(@"Native TextInput(%@) is %zd events ahead of JS - try to make your JS faster.", self.text, eventLag);
   }