Fix preload for React v16.3.1.

jaydenseric · jaydenseric · commit effac1b03ad7 · 2018-04-04T11:44:55.000+10:00
See facebook/react#12501 (comment).
diff --git a/changelog.md b/changelog.md
@@ -3,6 +3,8 @@
 ## Next
 
 * Updated dependencies.
+* Updated the `react` peer dependency to `^16.3.1`.
+* Fixed `preload` broken due to the [React v16.3.1](https://github.com/facebook/react/releases/tag/v16.3.1) [context API change](https://github.com/facebook/react/pull/12501).
 * Example updates:
   * Valid length app manifest `short_name`.
   * Added `<html>` `lang` attribute.
diff --git a/package.json b/package.json
@@ -34,7 +34,7 @@
   },
   "browserslist": ">1%",
   "peerDependencies": {
-    "react": "^16.3.0-alpha.1"
+    "react": "^16.3.1"
   },
   "dependencies": {
     "extract-files": "^3.1.0",
diff --git a/src/preload.mjs b/src/preload.mjs
@@ -111,8 +111,8 @@ export function preload(element) {
         element.props.children
       ) {
         // If the element is a context provider first set the value.
-        if (element.type.context)
-          element.type.context.currentValue = element.props.value
+        if (element.type._context)
+          element.type._context.currentValue = element.props.value
 
         recurse(element.props.children, legacyContext)
       }
