Add property to force HW acceleration on Android for modal windows

Summary:
When using React Native on Android on top of a game as an overlay, dialog windows sometimes get created with hardware acceleration disabled. This causes the UI to be unresponsive and anything that uses a TextureView stops working. Added a property for the modal view to make sure hardware acceleration flag is enabled when it's set to true.

**Test plan (required)**

set `hardwareAccelerated` property for Modal to force hardware acceleration on dialog windows on Android. Does nothing on iOS.
Closes https://github.com/facebook/react-native/pull/11421

Differential Revision: D4312912

Pulled By: andreicoman11

fbshipit-source-id: 9db6b2eca361421b92b24234b3501b5de0eecea7

Libraries/Modal/Modal.js

@@ -93,6 +93,11 @@ class Modal extends React.Component {
      * The `transparent` prop determines whether your modal will fill the entire view. Setting this to `true` will render the modal over a transparent background.
      */
     transparent: PropTypes.bool,
+    /**
+     * The `hardwareAccelerated` prop controls whether to force hardware acceleration for the underlying window.
+     * @platform android
+     */
+    hardwareAccelerated: PropTypes.bool,
     /**
      * The `visible` prop determines whether your modal is visible.
      */
@@ -126,6 +131,7 @@ class Modal extends React.Component {
 
   static defaultProps = {
     visible: true,
+    hardwareAccelerated: false,
   };
 
   static contextTypes = {
@@ -160,6 +166,7 @@ class Modal extends React.Component {
       <RCTModalHostView
         animationType={animationType}
         transparent={this.props.transparent}
+        hardwareAccelerated={this.props.hardwareAccelerated}
         onRequestClose={this.props.onRequestClose}
         onShow={this.props.onShow}
         style={styles.modal}