Cross platform ActivityIndicator

Summary:
The API for `ActivityIndiatorIOS` and `ProgressBarAndroid` is very similar and can be merged in a cross platform component that displays a circular indeterminate loading indicator.

This deprecates `ActivityIndiatorIOS` and non-horizontal `ProgressBarAndroid` in favor of this new component.

**Test plan (required)**

Tested with the ActivityIndicator example in UIExplorer on android and ios. Also made sure that `ActivityIndicatorIOS` still works and displays a deprecation warning. Also tested that `ProgressBarAndroid` with `indeterminate == true` and `styleAttr != 'Horizontal'` displays a deprecation warning.
Closes https://github.com/facebook/react-native/pull/6897

Differential Revision: D3351607

Pulled By: dmmiller

fbshipit-source-id: b107ce99d966359003e8b3118cd97b90fa1d3d7d

Examples/UIExplorer/ActivityIndicatorExample.js

@@ -0,0 +1,173 @@
+/**
+ * The examples provided by Facebook are for non-commercial testing and
+ * evaluation purposes only.
+ *
+ * Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON INFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * @flow
+ */
+'use strict';
+
+const React = require('react');
+const ReactNative = require('react-native');
+const {
+  ActivityIndicator,
+  StyleSheet,
+  View,
+} = ReactNative;
+const TimerMixin = require('react-timer-mixin');
+
+const ToggleAnimatingActivityIndicator = React.createClass({
+  mixins: [TimerMixin],
+
+  getInitialState() {
+    return {
+      animating: true,
+    };
+  },
+
+  setToggleTimeout() {
+    this.setTimeout(() => {
+      this.setState({animating: !this.state.animating});
+      this.setToggleTimeout();
+    }, 2000);
+  },
+
+  componentDidMount() {
+    this.setToggleTimeout();
+  },
+
+  render() {
+    return (
+      <ActivityIndicator
+        animating={this.state.animating}
+        style={[styles.centering, {height: 80}]}
+        size="large"
+      />
+    );
+  }
+});
+
+exports.displayName = (undefined: ?string);
+exports.framework = 'React';
+exports.title = '<ActivityIndicator>';
+exports.description = 'Animated loading indicators.';
+
+exports.examples = [
+  {
+    title: 'Default (small, white)',
+    render() {
+      return (
+        <ActivityIndicator
+          style={[styles.centering, styles.gray]}
+          color="white"
+        />
+      );
+    }
+  },
+  {
+    title: 'Gray',
+    render() {
+      return (
+        <View>
+          <ActivityIndicator
+            style={[styles.centering]}
+          />
+          <ActivityIndicator
+            style={[styles.centering, {backgroundColor: '#eeeeee'}]}
+          />
+        </View>
+      );
+    }
+  },
+  {
+    title: 'Custom colors',
+    render() {
+      return (
+        <View style={styles.horizontal}>
+          <ActivityIndicator color="#0000ff" />
+          <ActivityIndicator color="#aa00aa" />
+          <ActivityIndicator color="#aa3300" />
+          <ActivityIndicator color="#00aa00" />
+        </View>
+      );
+    }
+  },
+  {
+    title: 'Large',
+    render() {
+      return (
+        <ActivityIndicator
+          style={[styles.centering, styles.gray]}
+          color="white"
+          size="large"
+        />
+      );
+    }
+  },
+  {
+    title: 'Large, custom colors',
+    render() {
+      return (
+        <View style={styles.horizontal}>
+          <ActivityIndicator
+            size="large"
+            color="#0000ff"
+          />
+          <ActivityIndicator
+            size="large"
+            color="#aa00aa"
+          />
+          <ActivityIndicator
+            size="large"
+            color="#aa3300"
+          />
+          <ActivityIndicator
+            size="large"
+            color="#00aa00"
+          />
+        </View>
+      );
+    }
+  },
+  {
+    title: 'Start/stop',
+    render() {
+      return <ToggleAnimatingActivityIndicator />;
+    }
+  },
+  {
+    title: 'Custom size',
+    render() {
+      return (
+        <ActivityIndicator
+          style={[styles.centering, {transform: [{scale: 1.5}]}]}
+          size="large"
+        />
+      );
+    }
+  },
+];
+
+const styles = StyleSheet.create({
+  centering: {
+    alignItems: 'center',
+    justifyContent: 'center',
+    padding: 8,
+  },
+  gray: {
+    backgroundColor: '#cccccc',
+  },
+  horizontal: {
+    flexDirection: 'row',
+    justifyContent: 'space-around',
+    padding: 8,
+  },
+});