Implement TextInput.selectTextOnFocus for Android

Summary:Uses native Android `TextView.setSelectAllOnFocus` method. Triggers TextInput's `onSelectionChanged` event on focus as expected.
Closes https://github.com/facebook/react-native/pull/6654

Differential Revision: D3126354

Pulled By: mkonicek

fb-gh-sync-id: faa64314c0ddc87296277ccd707f18effef8f407
fbshipit-source-id: faa64314c0ddc87296277ccd707f18effef8f407

Libraries/Components/TextInput/TextInput.js

@@ -284,7 +284,6 @@ var TextInput = React.createClass({
     clearTextOnFocus: PropTypes.bool,
     /**
      * If true, all text will automatically be selected on focus
-     * @platform ios
      */
     selectTextOnFocus: PropTypes.bool,
     /**
@@ -524,6 +523,7 @@ var TextInput = React.createClass({
         underlineColorAndroid={this.props.underlineColorAndroid}
         children={children}
         editable={this.props.editable}
+        selectTextOnFocus={this.props.selectTextOnFocus}
       />;
 
     return (

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

@@ -209,6 +209,11 @@ public class ReactTextInputManager extends BaseViewManager<ReactEditText, Layout
     }
   }
 
+  @ReactProp(name = "selectTextOnFocus", defaultBoolean = false)
+  public void setSelectTextOnFocus(ReactEditText view, boolean selectTextOnFocus) {
+    view.setSelectAllOnFocus(selectTextOnFocus);
+  }
+
   @ReactProp(name = ViewProps.COLOR, customType = "Color")
   public void setColor(ReactEditText view, @Nullable Integer color) {
     if (color == null) {