Fix crash when opening account sync detail for external app

Bug: 32426306
Test: Manual, and added unit test
Change-Id: I8703c9a13a60e57d7dd2bab2ae3cf6be362e351a
(cherry picked from commit e3ad2b56c3)

src/com/android/settings/accounts/AccountPreferenceBase.java

@@ -33,10 +33,10 @@ import android.os.UserManager;
 import android.support.v7.preference.PreferenceScreen;
 import android.text.format.DateFormat;
 import android.util.Log;
-import android.view.ContextThemeWrapper;
 
 import com.android.settings.SettingsPreferenceFragment;
 import com.android.settings.Utils;
+import com.android.settings.utils.LocalClassLoaderContextThemeWrapper;
 import com.android.settingslib.accounts.AuthenticatorHelper;
 
 import java.util.ArrayList;
@@ -156,7 +156,8 @@ abstract class AccountPreferenceBase extends SettingsPreferenceFragment
                             desc.packageName, 0, mUserHandle);
                     final Theme baseTheme = getResources().newTheme();
                     baseTheme.applyStyle(com.android.settings.R.style.Theme_SettingsBase, true);
-                    final Context themedCtx = new ContextThemeWrapper(targetCtx, 0);
+                    final Context themedCtx =
+                            new LocalClassLoaderContextThemeWrapper(getClass(), targetCtx, 0);
                     themedCtx.getTheme().setTo(baseTheme);
                     prefs = getPreferenceManager().inflateFromResource(themedCtx,
                             desc.accountPreferencesId, parent);

src/com/android/settings/utils/LocalClassLoaderContextThemeWrapper.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.utils;
+
+import android.annotation.StyleRes;
+import android.content.Context;
+import android.view.ContextThemeWrapper;
+
+/**
+ * {@link ContextThemeWrapper} that provides a local classloader. This guarantees we have a
+ * valid {@link ClassLoader} when base context is from an external app.
+ */
+public class LocalClassLoaderContextThemeWrapper extends ContextThemeWrapper {
+
+    private Class mLocalClass;
+
+    public LocalClassLoaderContextThemeWrapper(Class clazz, Context base,
+            @StyleRes int themeResId) {
+        super(base, themeResId);
+        mLocalClass = clazz;
+    }
+
+    @Override
+    public ClassLoader getClassLoader() {
+        return mLocalClass.getClassLoader();
+    }
+}