Fixes AOSP crash when WPP isn't installed.

If there is no installed application with the ability to start an
activity with the SET_WALLPAPER action, we no longer show the
"Shortcuts" entry under the "Display > Lock screen" settings page.

Flag: CUSTOMIZABLE_LOCK_SCREEN_QUICK_AFFORDANCES
Fix: 274075866
Test: expanded unit test
Test: manually verified that, if Intent.resolveActivity returns false,
the shortcuts item isn't present in settings.

Change-Id: I919427d1e71a88a520c762307029a53065a68f46

src/com/android/settings/display/CustomizableLockScreenQuickAffordancesPreferenceController.java

@@ -50,7 +50,7 @@ public class CustomizableLockScreenQuickAffordancesPreferenceController extends
         final Preference preference = screen.findPreference(getPreferenceKey());
         if (preference != null) {
             preference.setOnPreferenceClickListener(preference1 -> {
-                final Intent intent = new Intent(Intent.ACTION_SET_WALLPAPER);
+                final Intent intent = CustomizableLockScreenUtils.newIntent();
                 final String packageName =
                         mContext.getString(R.string.config_wallpaper_picker_package);
                 if (!TextUtils.isEmpty(packageName)) {

src/com/android/settings/display/CustomizableLockScreenUtils.java

@@ -18,6 +18,8 @@ package com.android.settings.display;
 
 import android.content.ContentResolver;
 import android.content.Context;
+import android.content.Intent;
+import android.content.pm.PackageManager;
 import android.database.Cursor;
 import android.net.Uri;
 import android.text.TextUtils;
@@ -67,6 +69,10 @@ public final class CustomizableLockScreenUtils {
      * <p>This is a slow, blocking call that shouldn't be made on the main thread.
      */
     public static boolean isFeatureEnabled(Context context) {
+        if (!isWallpaperPickerInstalled(context)) {
+            return false;
+        }
+
         try (Cursor cursor = context.getContentResolver().query(
                 FLAGS_URI,
                 null,
@@ -151,4 +157,17 @@ public final class CustomizableLockScreenUtils {
             return null;
         }
     }
+
+    /**
+     * Returns a new {@link Intent} that can be used to start the wallpaper picker
+     * activity.
+     */
+    public static Intent newIntent() {
+        return new Intent(Intent.ACTION_SET_WALLPAPER);
+    }
+
+    private static boolean isWallpaperPickerInstalled(Context context) {
+        final PackageManager packageManager = context.getPackageManager();
+        return newIntent().resolveActivity(packageManager) != null;
+    }
 }