Enable deep-linking from notifications for recently used web apps on the Android home screen.

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappLauncherActivity.java

 // Copyright 2015 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.chrome.browser.webapps;
 
 import android.app.Activity;
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Build;
 import android.os.Bundle;
 import android.util.Base64;
 
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.Log;
+import org.chromium.chrome.browser.IntentHandler;
 import org.chromium.chrome.browser.ShortcutHelper;
 import org.chromium.chrome.browser.document.ChromeLauncherActivity;
 import org.chromium.chrome.browser.metrics.LaunchMetrics;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.util.IntentUtils;
 
 import java.lang.ref.WeakReference;
 
 /**
  * Launches web apps.  This was separated from the ChromeLauncherActivity because the
@@ skipping 24 matching lines @@
         String webappUrl = webappInfo.uri().toString();
         int webappSource = webappInfo.source();
 
         if (webappId != null && webappUrl != null) {
             String webappMacString = IntentUtils.safeGetStringExtra(
                     intent, ShortcutHelper.EXTRA_MAC);
             byte[] webappMac =
                     webappMacString == null ? null : Base64.decode(webappMacString, Base64.DEFAULT);
 
             Intent launchIntent = null;
-            if (webappMac != null && WebappAuthenticator.isUrlValid(this, webappUrl, webappMac)) {
+
+            // Permit the launch to a standalone web app frame if the intent was sent by Chrome, or
+            // if the MAC is present and valid for the URL to be opened.
+            boolean isTrusted = IntentHandler.wasIntentSenderChrome(intent,
+                    ApplicationStatus.getApplicationContext());
+            boolean isUrlValid = (webappMac != null
+                    && WebappAuthenticator.isUrlValid(this, webappUrl, webappMac));
+
+            if (isTrusted || isUrlValid) {
                 LaunchMetrics.recordHomeScreenLaunchIntoStandaloneActivity(webappUrl, webappSource);
 
                 String activityName = WebappActivity.class.getName();
                 if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
                     // Specifically assign the app to a particular WebappActivity instance.
                     int activityIndex = ActivityAssigner.instance(this).assign(webappId);
                     activityName += String.valueOf(activityIndex);
                 }
 
                 // Create an intent to launch the Webapp in an unmapped WebappActivity.
@@ skipping 41 matching lines @@
                     && webappActivity.getActivityTab().getId() == tabId) {
                 Tab tab = webappActivity.getActivityTab();
                 tab.getTabWebContentsDelegateAndroid().activateContents();
                 return true;
             }
         }
 
         return false;
     }
 }