Native implementation of <Image> intrinsic content size on iOS

Summary:
Now intrinsic content size of <Image> is implemented natively on iOS and now it is actually
`intrinsicContentSize`, not just overrided `height` and `width` styles (which was incorrect and hacky).
This change also removes support of nested content inside <Image>.
This is a first commit in the row where we improve <Image> implementation.

Reviewed By: mmmulani

Differential Revision: D5189017

fbshipit-source-id: eab3defa3d86a5d4219b4f4925ab7460b58d760f

Libraries/Image/Image.ios.js

@@ -352,13 +352,11 @@ const Image = createReactClass({
     const source = resolveAssetSource(this.props.source) || { uri: undefined, width: undefined, height: undefined };
 
     let sources;
-    let style;
+    let style = flattenStyle([styles.base, this.props.style]) || {};
     if (Array.isArray(source)) {
-      style = flattenStyle([styles.base, this.props.style]) || {};
       sources = source;
     } else {
-      const {width, height, uri} = source;
-      style = flattenStyle([{width, height}, styles.base, this.props.style]) || {};
+      const {uri} = source;
       sources = [source];
 
       if (uri === '') {

Libraries/Image/RCTImageView.m

@@ -13,6 +13,7 @@
 #import <React/RCTConvert.h>
 #import <React/RCTEventDispatcher.h>
 #import <React/RCTImageSource.h>
+#import <React/RCTUIManager.h>
 #import <React/RCTUtils.h>
 #import <React/UIView+React.h>
 
@@ -107,6 +108,22 @@ static NSDictionary *onLoadParamsForSource(RCTImageSource *source)
 
 RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
+- (CGSize)intrinsicContentSize
+{
+  // The first `imageSource` defines intrinsic content size.
+  RCTImageSource *imageSource = _imageSources.firstObject;
+  if (!imageSource) {
+    return CGSizeZero;
+  }
+
+  return imageSource.size;
+}
+
+- (void)updateIntrinsicContentSize
+{
+  [_bridge.uiManager setIntrinsicContentSize:self.intrinsicContentSize forView:self];
+}
+
 - (void)updateWithImage:(UIImage *)image
 {
   if (!image) {
@@ -176,6 +193,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 {
   if (![imageSources isEqual:_imageSources]) {
     _imageSources = [imageSources copy];
+    [self updateIntrinsicContentSize];
     _needsReload = YES;
   }
 }