Allow "freezing" NativePages to spare up memory.

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 b5f61272ab0b41250125609c70240133a214827a..8707776759627e50639af48b1200224616730c53 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/Tab.java
@@ -707,6 +707,16 @@ public class Tab implements NavigationClient {
     }
 
     /**
+     * Replaces the current NativePage with a empty stand-in for a NativePage. This can be used
+     * to reduce memory pressure.
+     */
+    public void freezeNativePage() {
+        if (mNativePage == null || mNativePage instanceof FrozenNativePage) return;
+        assert mNativePage.getView().getParent() == null : "Cannot freeze visible native page";
+        mNativePage = FrozenNativePage.freeze(mNativePage);
+    }
+
+    /**
      * Hides the current {@link NativePage}, if any, and shows the {@link ContentViewCore}'s view.
      */
     protected void showRenderedPage() {