Add UI for mainline modules licenses.

Added a module licenses option that lives in Legal information settings.
Clicking that option opens module licenses page, which displays every
module by name, filtered to exclude modules without license files.
Clicking a module in the list opens HTMLViewer.

Created ModuleLicensesProvider, a new ContentProvider that serves as a
redirect for the Uris sent to HTMLViewer so that they open asset files.
In order to provide the redirect, the provider will write the license file
to a file in Settings' cache directory when the license does not exist
in the cache or is outdated. The provider then opens that cached file.

Fixes: 135183006
Test: robotests
Change-Id: I7d69da34780c8c4efb150d0c0411078c12bc80d8

src/com/android/settings/deviceinfo/legal/ModuleLicensesPreferenceController.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2019 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.deviceinfo.legal;
+
+import android.content.Context;
+import android.content.pm.ModuleInfo;
+import android.content.pm.PackageManager;
+
+import androidx.preference.PreferenceGroup;
+import androidx.preference.PreferenceScreen;
+
+import com.android.internal.util.ArrayUtils;
+import com.android.settings.core.BasePreferenceController;
+
+import java.io.IOException;
+import java.util.Comparator;
+import java.util.List;
+
+public class ModuleLicensesPreferenceController extends BasePreferenceController {
+    public ModuleLicensesPreferenceController(Context context, String preferenceKey) {
+        super(context, preferenceKey);
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return AVAILABLE_UNSEARCHABLE;
+    }
+
+    @Override
+    public void displayPreference(PreferenceScreen screen) {
+        super.displayPreference(screen);
+
+        PackageManager packageManager = mContext.getPackageManager();
+        List<ModuleInfo> modules = packageManager.getInstalledModules(0 /* flags */);
+        PreferenceGroup group = screen.findPreference(getPreferenceKey());
+        modules.stream()
+                .sorted(Comparator.comparing(o -> o.getName().toString()))
+                .filter(new Predicate(mContext))
+                .forEach(module ->
+                        group.addPreference(
+                                new ModuleLicensePreference(group.getContext(), module)));
+    }
+
+    static class Predicate implements java.util.function.Predicate<ModuleInfo> {
+        private final Context mContext;
+
+        public Predicate(Context context) {
+            mContext = context;
+        }
+        @Override
+        public boolean test(ModuleInfo module) {
+            try {
+                return ArrayUtils.contains(
+                        ModuleLicenseProvider.getPackageAssetManager(
+                                mContext.getPackageManager(),
+                                module.getPackageName())
+                                        .list(""),
+                        ModuleLicenseProvider.GZIPPED_LICENSE_FILE_NAME);
+            } catch (IOException | PackageManager.NameNotFoundException e) {
+                return false;
+            }
+        }
+    }
+}