getInstalledRelatedApps: Avoid blocking the UI thread doing computation.

content/public/android/java/src/org/chromium/content/browser/installedapp/InstalledAppProviderImpl.java

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.content.browser.installedapp;
 
 import android.content.Context;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.res.Resources;
+import android.os.AsyncTask;
 
 import org.json.JSONArray;
 import org.json.JSONException;
 import org.json.JSONObject;
 
 import org.chromium.base.Log;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.installedapp.mojom.InstalledAppProvider;
 import org.chromium.installedapp.mojom.RelatedApplication;
 import org.chromium.mojo.system.MojoException;
@@ skipping 39 matching lines @@
         public boolean isIncognito();
     }
 
     public InstalledAppProviderImpl(FrameUrlDelegate frameUrlDelegate, Context context) {
         mFrameUrlDelegate = frameUrlDelegate;
         mContext = context;
     }
 
     @Override
     public void filterInstalledApps(
-            RelatedApplication[] relatedApps, FilterInstalledAppsResponse callback) {
+            final RelatedApplication[] relatedApps, final FilterInstalledAppsResponse callback) {
         if (mFrameUrlDelegate.isIncognito()) {
             callback.call(new RelatedApplication[0]);
             return;
         }
 
-        URI frameUrl = mFrameUrlDelegate.getUrl();
+        final URI frameUrl = mFrameUrlDelegate.getUrl();
+
+        // Use an AsyncTask to execute the installed/related checks on a background thread (so as
+        // not to block the UI thread).
+        new AsyncTask<Void, Void, RelatedApplication[]>() {
+            @Override
+            protected RelatedApplication[] doInBackground(Void... unused) {
+                return filterInstalledAppsOnBackgroundThread(relatedApps, frameUrl);
+            }
+
+            @Override
+            protected void onPostExecute(RelatedApplication[] installedApps) {
+                callback.call(installedApps);
+            }
+        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+    }
+
+    @Override
+    public void close() {}
+
+    @Override
+    public void onConnectionError(MojoException e) {}
+
+    /**
+     * Filters a list of apps, returning those that are both installed and match the origin.
+     *
+     * This method is expected to be called on a background thread (not the main UI thread).
+     *
+     * @param relatedApps A list of applications to be filtered.
+     * @param frameUrl The URL of the frame this operation was called from.
+     * @return A subsequence of applications that meet the criteria.
+     */
+    private RelatedApplication[] filterInstalledAppsOnBackgroundThread(
+            RelatedApplication[] relatedApps, URI frameUrl) {
         ArrayList<RelatedApplication> installedApps = new ArrayList<RelatedApplication>();
         PackageManager pm = mContext.getPackageManager();
         for (RelatedApplication app : relatedApps) {
             // If the package is of type "play", it is installed, and the origin is associated with
             // package, add the package to the list of valid packages.
             // NOTE: For security, it must not be possible to distinguish (from the response)
             // between the app not being installed and the origin not being associated with the app
             // (otherwise, arbitrary websites would be able to test whether un-associated apps are
             // installed on the user's device).
             if (app.platform.equals(RELATED_APP_PLATFORM_ANDROID) && app.id != null
                     && isAppInstalledAndAssociatedWithOrigin(app.id, frameUrl, pm)) {
                 installedApps.add(app);
             }
         }
 
         RelatedApplication[] installedAppsArray = new RelatedApplication[installedApps.size()];
         installedApps.toArray(installedAppsArray);
-        callback.call(installedAppsArray);
+        return installedAppsArray;
     }
 
-    @Override
-    public void close() {}
-
-    @Override
-    public void onConnectionError(MojoException e) {}
-
     /**
      * Determines whether a particular app is installed and matches the origin.
      *
      * @param packageName Name of the Android package to check if installed. Returns false if the
      *                    app is not installed.
      * @param frameUrl Returns false if the Android package does not declare association with the
      *                origin of this URL. Can be null.
      */
     private static boolean isAppInstalledAndAssociatedWithOrigin(
             String packageName, URI frameUrl, PackageManager pm) {
@@ skipping 127 matching lines @@
 
     private static boolean statementTargetMatches(URI frameUrl, URI assetUrl) {
         if (assetUrl.getScheme() == null || assetUrl.getAuthority() == null) {
             return false;
         }
 
         return assetUrl.getScheme().equals(frameUrl.getScheme())
                 && assetUrl.getAuthority().equals(frameUrl.getAuthority());
     }
 }