Use SL RadioButton for Search Engine pref

The AppCompat bug that made this workaround necessary (see original bug:
https://crbug.com/474695) was fixed >4 years. Cleaning up now that it's
no longer applicable.

Tested UI on KitKat, Lollipop and Pie.

Change-Id: I6fb6b73a2c96d8d4fab0ef28710503011e86e77a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1747030Reviewed-by: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Natalie Chouinard <chouinard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686135}

chrome/android/java/res/layout/search_engine.xml

@@ -12,7 +12,7 @@
     android:focusable="true"
     android:padding="6dp">
 
-    <android.widget.RadioButton
+    <RadioButton
         android:id="@+id/radiobutton"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"

chrome/android/java/src/org/chromium/chrome/browser/preferences/SearchEngineAdapter.java

@@ -6,7 +6,6 @@ package org.chromium.chrome.browser.preferences;
 
 import android.content.Context;
 import android.content.res.Resources;
-import android.os.Build;
 import android.support.annotation.IntDef;
 import android.support.annotation.StringRes;
 import android.text.SpannableString;
@@ -364,18 +363,8 @@ public class SearchEngineAdapter extends BaseAdapter
         view.setOnClickListener(this);
         view.setTag(position);
 
-        // TODO(finnur): There's a tinting bug in the AppCompat lib (see http://crbug.com/474695),
-        // which causes the first radiobox to always appear selected, even if it is not. It is being
-        // addressed, but in the meantime we should use the native RadioButton instead.
-        RadioButton radioButton = (RadioButton) view.findViewById(R.id.radiobutton);
-        // On Lollipop this removes the redundant animation ring on selection but on older versions
-        // it would cause the radio button to disappear.
-        // TODO(finnur): Remove the encompassing if statement once we go back to using the AppCompat
-        // control.
+        RadioButton radioButton = view.findViewById(R.id.radiobutton);
         final boolean selected = position == mSelectedSearchEnginePosition;
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
-            radioButton.setBackgroundResource(0);
-        }
         radioButton.setChecked(selected);
 
         TextView description = (TextView) view.findViewById(R.id.name);