Set the linter target for awwebcontentsdelegateadapter class

Set the target API for the class to 21 (lollipop) which is what is supported
by updatable webview. This prevents us individually suppress lint messages.

BUG=

Review URL: https://codereview.chromium.org/1704263002

Cr-Commit-Position: refs/heads/master@{#376057}

android_webview/java/src/org/chromium/android_webview/AwWebContentsDelegateAdapter.java

@@ -4,12 +4,13 @@
 
 package org.chromium.android_webview;
 
-import android.annotation.SuppressLint;
+import android.annotation.TargetApi;
 import android.content.ContentResolver;
 import android.content.Context;
 import android.media.AudioManager;
 import android.net.Uri;
 import android.os.AsyncTask;
+import android.os.Build;
 import android.os.Handler;
 import android.os.Message;
 import android.provider.MediaStore;
@@ -29,6 +30,7 @@ import org.chromium.content_public.browser.InvalidateTypes;
  * This class also serves a secondary function of routing certain callbacks from the content layer
  * to specific listener interfaces.
  */
+@TargetApi(Build.VERSION_CODES.LOLLIPOP)
 class AwWebContentsDelegateAdapter extends AwWebContentsDelegate {
     private static final String TAG = "AwWebContentsDelegateAdapter";
 
@@ -111,7 +113,6 @@ class AwWebContentsDelegateAdapter extends AwWebContentsDelegate {
         }
     }
 
-    @SuppressLint("NewApi")  // View#getLayoutDirection requires API level 17.
     @Override
     public boolean takeFocus(boolean reverse) {
         int direction =