Use AndroidX's @VisibleForTesting in feed.

Chromium's only exists for historic reasons, currently serving
documentation purposes only. AndroidX's version is supported by
Android lint, though the check at build time is not currently
working (crbug.com/1022939). This check is still useful for
Android Studio.

These instances were missed in
https://chromium-review.googlesource.com/c/chromium/src/+/1901635.

Bug: 889467
Change-Id: I39e5a2039a7eb7ac29d1e5d35e9d22af7c60e951
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1907199Reviewed-by: Carlos Knippschild <carlosk@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714934}

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/FeedNewTabPage.java

@@ -11,10 +11,11 @@ import android.view.LayoutInflater;
 import android.view.MotionEvent;
 import android.view.View;
 
+import androidx.annotation.VisibleForTesting;
+
 import com.google.android.libraries.feed.api.client.stream.Stream;
 import com.google.android.libraries.feed.api.host.action.ActionApi;
 
-import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.ActivityTabProvider;
 import org.chromium.chrome.browser.ChromeActivity;

chrome/android/feed/core/java/src/org/chromium/chrome/browser/feed/TestNetworkClient.java

@@ -6,6 +6,8 @@ package org.chromium.chrome.browser.feed;
 
 import android.util.Base64;
 
+import androidx.annotation.VisibleForTesting;
+
 import com.google.android.libraries.feed.api.host.config.Configuration;
 import com.google.android.libraries.feed.api.host.network.HttpRequest;
 import com.google.android.libraries.feed.api.host.network.HttpRequest.HttpMethod;
@@ -23,7 +25,6 @@ import com.google.search.now.wire.feed.ResponseProto.Response;
 import com.google.search.now.wire.feed.mockserver.MockServerProto.ConditionalResponse;
 import com.google.search.now.wire.feed.mockserver.MockServerProto.MockServer;
 
-import org.chromium.base.VisibleForTesting;
 import org.chromium.base.task.PostTask;
 import org.chromium.content_public.browser.UiThreadTaskTraits;