select up and down the inspector hierarchy

Summary:
This allows you to select the displayed owner hierarchy, and see the styles,
props, and position.

@public

Test Plan:
Open the inspector, select something in the middle of the page. Click the
breadcrumb train in the inspector, and verify that:
- styles are reflected
- margin/padding/box is correct
- the highlight updates to show the selected item

See video as well.

[Video](https://www.latest.facebook.com/pxlcld/mqnl)

Screenshot
{F22518618}

Libraries/ReactIOS/InspectorOverlay/ElementProperties.js

@@ -18,38 +18,79 @@ var View = require('View');
 var PropTypes = require('ReactPropTypes');
 var BoxInspector = require('BoxInspector');
 var StyleInspector = require('StyleInspector');
+var TouchableHighlight = require('TouchableHighlight');
+var TouchableWithoutFeedback = require('TouchableWithoutFeedback');
 
 var flattenStyle = require('flattenStyle');
+var mapWithSeparator = require('mapWithSeparator');
 
 var ElementProperties = React.createClass({
   propTypes: {
     hierarchy: PropTypes.array.isRequired,
     style: PropTypes.array.isRequired,
   },
+
   render: function() {
     var style = flattenStyle(this.props.style);
-    var path = this.props.hierarchy.map((instance) => {
-      return instance.getName ? instance.getName() : 'Unknown';
-    }).join(' > ');
+    var selection = this.props.selection;
+    // Without the `TouchableWithoutFeedback`, taps on this inspector pane
+    // would change the inspected element to whatever is under the inspector
     return (
+      <TouchableWithoutFeedback>
         <View style={styles.info}>
-        <Text style={styles.path}>
-          {path}
+          <View style={styles.breadcrumb}>
+            {mapWithSeparator(
+              this.props.hierarchy,
+              (item, i) => (
+                <TouchableHighlight
+                  style={[styles.breadItem, i === selection && styles.selected]}
+                  onPress={() => this.props.setSelection(i)}>
+                  <Text style={styles.breadItemText}>
+                    {item.getName ? item.getName() : 'Unknown'}
                   </Text>
+                </TouchableHighlight>
+              ),
+              () => <Text style={styles.breadSep}>&#9656;</Text>
+            )}
+          </View>
           <View style={styles.row}>
             <StyleInspector style={style} />
             <BoxInspector style={style} frame={this.props.frame} />
           </View>
         </View>
+      </TouchableWithoutFeedback>
     );
   }
 });
 
 var styles = StyleSheet.create({
+  breadSep: {
+    fontSize: 8,
+    color: 'white',
+  },
+  breadcrumb: {
+    flexDirection: 'row',
+    flexWrap: 'wrap',
+    marginBottom: 5,
+  },
+  selected: {
+    borderColor: 'white',
+    borderRadius: 5,
+  },
+  breadItem: {
+    borderWidth: 1,
+    borderColor: 'transparent',
+    marginHorizontal: 2,
+  },
+  breadItemText: {
+    fontSize: 10,
+    color: 'white',
+    marginHorizontal: 5,
+  },
   row: {
     flexDirection: 'row',
     alignItems: 'center',
-    justifyContent: 'space-around',
+    justifyContent: 'space-between',
   },
   info: {
     backgroundColor: 'rgba(0, 0, 0, 0.7)',

Libraries/ReactIOS/InspectorOverlay/InspectorOverlay.js

@@ -24,7 +24,9 @@ var InspectorOverlay = React.createClass({
   getInitialState: function() {
     return {
       frame: null,
+      pointerY: 0,
       hierarchy: [],
+      selection: -1,
     };
   },
 
@@ -42,6 +44,8 @@ var InspectorOverlay = React.createClass({
         var publicInstance = instance.getPublicInstance();
         this.setState({
           hierarchy,
+          pointerY: locationY,
+          selection: hierarchy.length - 1,
           frame: {left, top, width, height},
           style: publicInstance.props ? publicInstance.props.style : {},
         });
@@ -49,6 +53,18 @@ var InspectorOverlay = React.createClass({
     );
   },
 
+  setSelection(i) {
+    var instance = this.state.hierarchy[i];
+    var publicInstance = instance.getPublicInstance();
+    UIManager.measure(React.findNodeHandle(instance), (x, y, width, height, left, top) => {
+      this.setState({
+        frame: {left, top, width, height},
+        style: publicInstance.props ? publicInstance.props.style : {},
+        selection: i,
+      });
+    });
+  },
+
   shouldSetResponser: function(e) {
     this.findViewForTouchEvent(e);
     return true;
@@ -59,9 +75,8 @@ var InspectorOverlay = React.createClass({
     var justifyContent = 'flex-end';
 
     if (this.state.frame) {
-      var distanceToTop = this.state.frame.top;
-      var distanceToBottom = Dimensions.get('window').height -
-        (this.state.frame.top + this.state.frame.height);
+      var distanceToTop = this.state.pointerY;
+      var distanceToBottom = Dimensions.get('window').height - distanceToTop;
 
       justifyContent = distanceToTop > distanceToBottom
         ? 'flex-start'
@@ -73,6 +88,8 @@ var InspectorOverlay = React.createClass({
           style={this.state.style}
           frame={this.state.frame}
           hierarchy={this.state.hierarchy}
+          selection={this.state.selection}
+          setSelection={this.setSelection}
         />
       );
     } else {

Libraries/Utilities/mapWithSeparator.js

@@ -0,0 +1,19 @@
+/**
+ * Copyright 2004-present Facebook. All Rights Reserved.
+ *
+ * @providesModule mapWithSeparator
+ */
+'use strict';
+
+function mapWithSeparator(array, valueFunction, separatorFunction) {
+  var results = [];
+  for (var i = 0; i < array.length; i++) {
+    results.push(valueFunction(array[i], i, array));
+    if (i !== array.length - 1) {
+      results.push(separatorFunction(i));
+    }
+  }
+  return results;
+}
+
+module.exports = mapWithSeparator;