Fallback to default wallpaper picker if first choice fails

- Add fallback logic in WallpaperSuggestionActivity
- Move some classes around
- Delete some unused class

Change-Id: Ifc8864428647a94f3ecae50d193c2156b2592ff3
Fix: 36140287
Test: make RunSettingsRoboTests

src/com/android/settings/search/SearchIndexableResources.java

@@ -20,17 +20,16 @@ import android.provider.SearchIndexableResource;
 import android.support.annotation.DrawableRes;
 import android.support.annotation.VisibleForTesting;
 import android.support.annotation.XmlRes;
+
 import com.android.settings.DateTimeSettings;
 import com.android.settings.DevelopmentSettings;
 import com.android.settings.DeviceInfoSettings;
 import com.android.settings.DisplaySettings;
 import com.android.settings.EncryptionAndCredential;
 import com.android.settings.LegalSettings;
-import com.android.settings.PrivacySettings;
 import com.android.settings.R;
 import com.android.settings.ScreenPinningSettings;
 import com.android.settings.SecuritySettings;
-import com.android.settings.WallpaperTypeSettings;
 import com.android.settings.accessibility.AccessibilitySettings;
 import com.android.settings.accounts.UserAndAccountDashboardFragment;
 import com.android.settings.applications.AdvancedAppSettings;
@@ -76,6 +75,7 @@ import com.android.settings.system.SystemDashboardFragment;
 import com.android.settings.tts.TtsEnginePreferenceFragment;
 import com.android.settings.tts.TtsSlidersFragment;
 import com.android.settings.users.UserSettings;
+import com.android.settings.wallpaper.WallpaperTypeSettings;
 import com.android.settings.wifi.ConfigureWifiSettings;
 import com.android.settings.wifi.SavedAccessPointsWifiSettings;
 import com.android.settings.wifi.WifiSettings;