Fixed new line and prioritise blurOnSubmit in multiline text input

Summary:
What existing problem does the pull request solve?
this fixes #13506 and #12717 where:
- there are some issues when pressing enter with some keyboard
- blurOnSubmit is not working with multiline

I think this should be in stable branch as this is pretty critical, isn't it?

- just create a TextInput with multiline and press enter with samsung keyboard
before, it won't create a new line, now it will.

- just create a TextInput with multiline and blurOnSubmit true and press enter
before, it won't blur, and wont create a new line (on some keyboard, it will create a new line), now it will blur only
Closes https://github.com/facebook/react-native/pull/13890

Reviewed By: achen1

Differential Revision: D5333464

Pulled By: shergin

fbshipit-source-id: a0597d1b1967d4de1486e728e03160e1bb15afeb

ReactAndroid/src/main/java/com/facebook/react/views/textinput/ReactTextInputManager.java

@@ -728,16 +728,29 @@ public class ReactTextInputManager extends BaseViewManager<ReactEditText, Layout
             // Any 'Enter' action will do
             if ((actionId & EditorInfo.IME_MASK_ACTION) > 0 ||
                 actionId == EditorInfo.IME_NULL) {
-              EventDispatcher eventDispatcher =
-                  reactContext.getNativeModule(UIManagerModule.class).getEventDispatcher();
-              eventDispatcher.dispatchEvent(
-                  new ReactTextInputSubmitEditingEvent(
-                      editText.getId(),
-                      editText.getText().toString()));
-            }
+              boolean blurOnSubmit = editText.getBlurOnSubmit();
+              boolean isMultiline = ((editText.getInputType() &
+                InputType.TYPE_TEXT_FLAG_MULTI_LINE) != 0);
 
-            if (editText.getBlurOnSubmit()) {
-              editText.clearFocus();
+              // Motivation:
+              // * blurOnSubmit && isMultiline => Generate `submit` event; clear focus; prevent default behaviour (return true);
+              // * blurOnSubmit && !isMultiline => Generate `submit` event; clear focus; prevent default behaviour (return true);
+              // * !blurOnSubmit && isMultiline => Perform default behaviour (return false);
+              // * !blurOnSubmit && !isMultiline => Prevent default behaviour (return true).
+
+              if (blurOnSubmit) {
+                EventDispatcher eventDispatcher =
+                    reactContext.getNativeModule(UIManagerModule.class).getEventDispatcher();
+
+                eventDispatcher.dispatchEvent(
+                    new ReactTextInputSubmitEditingEvent(
+                        editText.getId(),
+                        editText.getText().toString()));
+
+                editText.clearFocus();
+              }
+
+              return blurOnSubmit || !isMultiline;
             }
 
             return true;