Prevent navigations within fullscreen webapps from being intercepted.

chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.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.externalnav;
 
 import android.content.ActivityNotFoundException;
 import android.content.ComponentName;
 import android.content.Intent;
 import android.content.pm.ResolveInfo;
@@ skipping 198 matching lines @@
             if (handler.isFromCustomTabIntent()) {
                 // http://crbug.com/613667 : Custom tabs forbids external navigation for the first
                 // url, unless the first url is a redirect.
                 if (!params.isRedirect()) return OverrideUrlLoadingResult.NO_OVERRIDE;
             } else if (handler.shouldStayInChrome(isExternalProtocol)
                     || handler.shouldNotOverrideUrlLoading()) {
                 return OverrideUrlLoadingResult.NO_OVERRIDE;
             }
         }
 
+        // http://crbug.com/647569 : Stay in a PWA window for a URL within the same scope.
+        if (mDelegate.isWithinCurrentWebappScope(params.getUrl())) {
+            return OverrideUrlLoadingResult.NO_OVERRIDE;
+        }
+
         // http://crbug.com/149218: We want to show the intent picker for ordinary links, providing
         // the link is not an incoming intent from another application, unless it's a redirect (see
         // below).
         boolean linkNotFromIntent = isLink && !isFromIntent;
 
         boolean isOnEffectiveIntentRedirect = params.getRedirectHandler() == null ? false
                 : params.getRedirectHandler().isOnEffectiveIntentRedirectChain();
 
         // http://crbug.com/170925: We need to show the intent picker when we receive an intent from
         // another app that 30x redirects to a YouTube/Google Maps/Play Store/Google+ URL etc.
@@ skipping 302 matching lines @@
         if (defaultSmsPackageName == null) return null;
         // Makes sure that the default SMS app actually resolves the intent.
         for (ResolveInfo resolveInfo : resolvingComponentNames) {
             if (defaultSmsPackageName.equals(resolveInfo.activityInfo.packageName)) {
                 return defaultSmsPackageName;
             }
         }
         return null;
     }
 }