Send key when onKeyPress event is fired from TextInput

Summary:
Changelog: [Internal]

In `onKeyPress` event, we were not returning `key` property. This diff adds `key` property to `onKeyPress` event and removes other, redundant properties from `onKeyPress` event.

The implementation has been translated from Paper.

Reviewed By: shergin

Differential Revision: D21250411

fbshipit-source-id: f1e31381667acb9dec02d0b33883df8f8f5b2a4b

React/Fabric/Mounting/ComponentViews/TextInput/RCTTextInputComponentView.mm

@@ -302,7 +302,10 @@ using namespace facebook::react;
 {
   if (!_backedTextInputView.textWasPasted) {
     if (_eventEmitter) {
-      std::static_pointer_cast<TextInputEventEmitter const>(_eventEmitter)->onKeyPress([self _textInputMetrics]);
+      KeyPressMetrics keyPressMetrics;
+      keyPressMetrics.text = RCTStringFromNSString(text);
+      keyPressMetrics.eventCount = _mostRecentEventCount;
+      std::static_pointer_cast<TextInputEventEmitter const>(_eventEmitter)->onKeyPress(keyPressMetrics);
     }
   }
 

ReactCommon/fabric/components/textinput/iostextinput/TextInputEventEmitter.cpp

@@ -37,6 +37,29 @@ static jsi::Value textInputMetricsPayload(
   return payload;
 };
 
+static jsi::Value keyPressMetricsPayload(
+    jsi::Runtime &runtime,
+    KeyPressMetrics const &keyPressMetrics) {
+  auto payload = jsi::Object(runtime);
+  payload.setProperty(runtime, "eventCount", keyPressMetrics.eventCount);
+
+  std::string key;
+  if (keyPressMetrics.text.empty()) {
+    key = "Backspace";
+  } else {
+    if (keyPressMetrics.text.front() == '\n') {
+      key = "Enter";
+    } else if (keyPressMetrics.text.front() == '\t') {
+      key = "Tab";
+    } else {
+      key = keyPressMetrics.text.front();
+    }
+  }
+  payload.setProperty(
+      runtime, "key", jsi::String::createFromUtf8(runtime, key));
+  return payload;
+};
+
 void TextInputEventEmitter::onFocus(
     TextInputMetrics const &textInputMetrics) const {
   dispatchTextInputEvent("focus", textInputMetrics);
@@ -78,8 +101,13 @@ void TextInputEventEmitter::onSubmitEditing(
 }
 
 void TextInputEventEmitter::onKeyPress(
-    TextInputMetrics const &textInputMetrics) const {
-  dispatchTextInputEvent("keyPress", textInputMetrics);
+    KeyPressMetrics const &keyPressMetrics) const {
+  dispatchEvent(
+      "keyPress",
+      [keyPressMetrics](jsi::Runtime &runtime) {
+        return keyPressMetricsPayload(runtime, keyPressMetrics);
+      },
+      EventPriority::AsynchronousBatched);
 }
 
 void TextInputEventEmitter::dispatchTextInputEvent(

ReactCommon/fabric/components/textinput/iostextinput/TextInputEventEmitter.h

@@ -25,6 +25,12 @@ class TextInputMetrics {
   int eventCount;
 };
 
+class KeyPressMetrics {
+ public:
+  std::string text;
+  int eventCount;
+};
+
 class TextInputEventEmitter : public ViewEventEmitter {
  public:
   using ViewEventEmitter::ViewEventEmitter;
@@ -37,7 +43,7 @@ class TextInputEventEmitter : public ViewEventEmitter {
   void onSelectionChange(TextInputMetrics const &textInputMetrics) const;
   void onEndEditing(TextInputMetrics const &textInputMetrics) const;
   void onSubmitEditing(TextInputMetrics const &textInputMetrics) const;
-  void onKeyPress(TextInputMetrics const &textInputMetrics) const;
+  void onKeyPress(KeyPressMetrics const &textInputMetrics) const;
 
  private:
   void dispatchTextInputEvent(