[change] Image - resolve onLoad with source

Use the same `nativeEvent` structure as in RN for the onLoad event

BREAKING CHANGE
`onLoad` was previously called with `nativeEvent` that was the browser Event object
from the image.onload handler
Since we can't spread or mutate the Event object to add `source` we have to
either add it under a new key or remove it
The browser Event does not expose very useful information, (no target, or size info),
so it seems best to replace `nativeEvent` with the same structure used in `react-native`

Author: kidroca

packages/react-native-web/src/exports/Image/index.js

@@ -320,14 +320,14 @@ const useSource = (
 
     return {
       // Use the resolved URI for cases where it was already loaded or preloaded
-      result: { uri },
+      result: { source: { uri } },
       status: ImageLoader.has(uri) ? LOADED : IDLE
     };
   });
 
   const handleLoad = React.useCallback(
     (result: ImageResult) => {
-      if (onLoad) onLoad(result);
+      if (onLoad) onLoad({ nativeEvent: result });
       if (onLoadEnd) onLoadEnd();
       setState({ status: LOADED, result });
     },
@@ -389,7 +389,7 @@ const useSource = (
 
   return {
     state: state.status,
-    loadedUri: state.result.uri
+    loadedUri: state.result.source.uri
   };
 };
 

packages/react-native-web/src/modules/ImageLoader/index.js

@@ -133,14 +133,15 @@ const ImageLoader = {
     id += 1;
     const image = new window.Image();
 
-    const handleLoad = (e) => {
+    const handleLoad = () => {
       // avoid blocking the main thread
       const onDecode = () =>
         onLoad({
-          nativeEvent: e,
-          uri: image.src,
-          width: image.naturalWidth,
-          height: image.naturalHeight
+          source: {
+            uri: image.src,
+            width: image.naturalWidth,
+            height: image.naturalHeight
+          }
         });
 
       // Safari currently throws exceptions when decoding svgs.

packages/react-native-web/src/modules/ImageLoader/types.js

@@ -14,8 +14,9 @@ export type ImageSource = {|
 |};
 
 export type ImageResult = {|
-  uri: string,
-  width: number,
-  height: number,
-  nativeEvent: Event
+  source: {
+    uri: string,
+    width: number,
+    height: number
+  }
 |};