Fix leaking NewTabPageView(s).

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
index 69275cf86e31a2ea24d982c7cc3f549fc27e95da..eba27fac1a8a81d136fc42d442cd78908d3dad65 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
@@ -334,6 +334,8 @@ public class NewTabPage
             public void onShown(Tab tab) {
                 // Showing the NTP is only meaningful when the page has been loaded already.
                 if (mIsLoaded) recordNTPShown();
+
+                mNewTabPageView.getTileGroup().onSwitchToForeground();
             }
 
             @Override