Remove mActivity from Tab and look at windowAndroid for tab

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

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivityTab.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivityTab.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivityTab.java
index 601189224089947fe9ae9d2b71b5e4d408b711a4..f8a7ee2d66ae1ef2eb332e46481af7b421175207 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivityTab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivityTab.java
@@ -315,9 +315,9 @@ public class FullScreenActivityTab extends ChromeTab {
             extends TabChromeWebContentsDelegateAndroid {
         @Override
         public void activateContents() {
-            if (!(mActivity instanceof WebappActivity)) return;
+            if (!(getActivity() instanceof WebappActivity)) return;
 
-            WebappInfo webappInfo = ((WebappActivity) mActivity).getWebappInfo();
+            WebappInfo webappInfo = ((WebappActivity) getActivity()).getWebappInfo();
             String url = webappInfo.uri().toString();
 
             // Create an Intent that will be fired toward the WebappLauncherActivity, which in turn
@@ -326,10 +326,11 @@ public class FullScreenActivityTab extends ChromeTab {
             // it the hard way.
             Intent intent = new Intent();
             intent.setAction(WebappLauncherActivity.ACTION_START_WEBAPP);
-            intent.setPackage(mActivity.getPackageName());
+            intent.setPackage(getApplicationContext().getPackageName());
             webappInfo.setWebappIntentExtras(intent);
 
-            intent.putExtra(ShortcutHelper.EXTRA_MAC, ShortcutHelper.getEncodedMac(mActivity, url));
+            intent.putExtra(ShortcutHelper.EXTRA_MAC,
+                    ShortcutHelper.getEncodedMac(getActivity(), url));
             intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
             getApplicationContext().startActivity(intent);
         }