Disable app install banners for custom tabs

chrome/android/java/src/org/chromium/chrome/browser/Tab.java

Index: chrome/android/java/src/org/chromium/chrome/browser/Tab.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/Tab.java b/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
index a8ad19c2b8b9296b9dc6fbce3aa14c1c9d8359c3..84d611ca10cdee7b84b3ff244bc86239f0c48960 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
@@ -1412,12 +1412,19 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
         initializeNative();
 
         if (AppBannerManager.isEnabled()) {
-            mAppBannerManager = new AppBannerManager(this, mContext);
-            addObserver(mAppBannerManager);
+            mAppBannerManager = createAppBannerManager();
+            if (mAppBannerManager != null) addObserver(mAppBannerManager);
         }
     }
 
     /**
+     * @return {@link AppBannerManager} to be used for this tab. May be null.
+     */
+    protected AppBannerManager createAppBannerManager() {
+        return new AppBannerManager(this, mContext);
+    }
+
+    /**
      * TODO(dtrainor): Remove after method is no longer used downstream.
      * Used to get a list of Android {@link View}s that represent both the normal content as well as
      * overlays.  This does not return {@link View}s for {@link NativePage}s.