Exposes the host container to prepareForCommit and resetAfterCommit

packages/react-reconciler/src/ReactFiberReconciler.js

@@ -93,8 +93,8 @@ export type HostConfig<T, P, I, TI, HI, PI, C, CC, CX, PL> = {
   ): number,
   cancelDeferredCallback(callbackID: number): void,
 
-  prepareForCommit(): void,
-  resetAfterCommit(): void,
+  prepareForCommit(containerInfo: C): void,
+  resetAfterCommit(containerInfo: C): void,
 
   now(): number,
 

packages/react-reconciler/src/ReactFiberScheduler.js

@@ -395,7 +395,7 @@ export default function<T, P, I, TI, HI, PI, C, CC, CX, PL>(
       firstEffect = finishedWork.firstEffect;
     }
 
-    prepareForCommit();
+    prepareForCommit(root.containerInfo);
 
     // Commit all the side-effects within a tree. We'll do this in two passes.
     // The first pass performs all the host insertions, updates, deletions and
@@ -434,7 +434,7 @@ export default function<T, P, I, TI, HI, PI, C, CC, CX, PL>(
     }
     stopCommitHostEffectsTimer();
 
-    resetAfterCommit();
+    resetAfterCommit(root.containerInfo);
 
     // The work-in-progress tree is now the current tree. This must come after
     // the first pass of the commit phase, so that the previous tree is still

packages/react-reconciler/src/__tests__/ReactFiberHostContext-test.js

@@ -64,4 +64,52 @@ describe('ReactFiberHostContext', () => {
     );
     expect(creates).toBe(2);
   });
+
+  it('should send the context to prepareForCommit and resetAfterCommit', () => {
+    let rootContext = {};
+    const Renderer = ReactFiberReconciler({
+      prepareForCommit: function(hostContext) {
+        expect(hostContext).toBe(rootContext);
+      },
+      resetAfterCommit: function(hostContext) {
+        expect(hostContext).toBe(rootContext);
+      },
+      getRootHostContext: function() {
+        return null;
+      },
+      getChildHostContext: function() {
+        return null;
+      },
+      shouldSetTextContent: function() {
+        return false;
+      },
+      createInstance: function() {
+        return null;
+      },
+      finalizeInitialChildren: function() {
+        return null;
+      },
+      appendInitialChild: function() {
+        return null;
+      },
+      now: function() {
+        return 0;
+      },
+      mutation: {
+        appendChildToContainer: function() {
+          return null;
+        },
+      },
+    });
+
+    const container = Renderer.createContainer(rootContext);
+    Renderer.updateContainer(
+      <a>
+        <b />
+      </a>,
+      container,
+      /* parentComponent: */ null,
+      /* callback: */ null,
+    );
+  });
 });