Use AndroidX's @VisibleForTesting in chromecast/

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.

Bug: 889467
Change-Id: I491efe7472e03cddfdc20009341955ed92bc7e81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1907194Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713956}

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastAudioManager.java

@@ -10,8 +10,9 @@ import android.media.audiopolicy.AudioPolicy;
 import android.os.Build;
 import android.support.annotation.Nullable;
 
+import androidx.annotation.VisibleForTesting;
+
 import org.chromium.base.Log;
-import org.chromium.base.VisibleForTesting;
 import org.chromium.chromecast.base.Controller;
 import org.chromium.chromecast.base.Observable;
 

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastCommandLineHelper.java

@@ -7,13 +7,14 @@ package org.chromium.chromecast.shell;
 import android.content.Intent;
 import android.content.SharedPreferences;
 
+import androidx.annotation.VisibleForTesting;
+
 import org.json.JSONException;
 import org.json.JSONObject;
 
 import org.chromium.base.CommandLine;
 import org.chromium.base.ContextUtils;
 import org.chromium.base.Log;
-import org.chromium.base.VisibleForTesting;
 import org.chromium.chromecast.base.Itertools;
 
 import java.util.concurrent.atomic.AtomicBoolean;

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/CastWebContentsComponent.java

@@ -13,8 +13,9 @@ import android.net.Uri;
 import android.os.IBinder;
 import android.os.PatternMatcher;
 
+import androidx.annotation.VisibleForTesting;
+
 import org.chromium.base.Log;
-import org.chromium.base.VisibleForTesting;
 import org.chromium.chromecast.base.Controller;
 import org.chromium.content_public.browser.WebContents;
 

chromecast/browser/android/apk/src/org/chromium/chromecast/shell/ElidedLogcatProvider.java

@@ -6,8 +6,9 @@ package org.chromium.chromecast.shell;
 
 import android.os.SystemClock;
 
+import androidx.annotation.VisibleForTesting;
+
 import org.chromium.base.Log;
-import org.chromium.base.VisibleForTesting;
 import org.chromium.base.task.AsyncTask;
 
 import java.io.BufferedReader;