[Android] Stop hiding the RWHV layer subtree when hiding the widget

ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java

Index: ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
diff --git a/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java b/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
index 5dfb5f168aced4442ba3ab16457d38f01d4df8aa..59108ce0fefcf6a919892ccbdccebeaa36ef2b55 100644
--- a/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
@@ -11,6 +11,8 @@ import android.content.Intent;
 import android.content.IntentSender.SendIntentException;
 import android.view.View;
 
+import org.chromium.base.ActivityState;
+import org.chromium.base.ApplicationStatus;
 import org.chromium.ui.UiUtils;
 
 import java.lang.ref.WeakReference;
@@ -20,7 +22,9 @@ import java.lang.ref.WeakReference;
  * Activity Instance.
  * Only instantiate this class when you need the implemented features.
  */
-public class ActivityWindowAndroid extends WindowAndroid implements View.OnLayoutChangeListener {
+public class ActivityWindowAndroid
+        extends WindowAndroid
+        implements ApplicationStatus.ActivityStateListener, View.OnLayoutChangeListener {
     // Constants used for intent request code bounding.
     private static final int REQUEST_CODE_PREFIX = 1000;
     private static final int REQUEST_CODE_RANGE_SIZE = 100;
@@ -29,10 +33,28 @@ public class ActivityWindowAndroid extends WindowAndroid implements View.OnLayou
     private final WeakReference<Activity> mActivityRef;
     private int mNextRequestCode = 0;
 
+    /**
+     * Creates an Activity-specific WindowAndroid with associated intent functionality.
+     * TODO(jdduke): Remove this overload when all callsites have been updated to
+     * indicate their activity state listening preference.
+     * @param activity The activity associated with the WindowAndroid.
+     */
     public ActivityWindowAndroid(Activity activity) {
+        this(activity, true);
+    }
+
+    /**
+     * Creates an Activity-specific WindowAndroid with associated intent functionality.
+     * @param activity The activity associated with the WindowAndroid.
+     * @param listenToActivityState Whether to listen to activity state changes.
+     */
+    public ActivityWindowAndroid(Activity activity, boolean listenToActivityState) {
         super(activity.getApplicationContext());
         mActivityRef = new WeakReference<Activity>(activity);
         activity.findViewById(android.R.id.content).addOnLayoutChangeListener(this);
+        if (listenToActivityState) {
+            ApplicationStatus.registerStateListenerForActivity(this, activity);
+        }
     }
 
     @Override
@@ -104,6 +126,15 @@ public class ActivityWindowAndroid extends WindowAndroid implements View.OnLayou
     }
 
     @Override
+    public void onActivityStateChange(Activity activity, int newState) {
+        if (newState == ActivityState.PAUSED) {
+            onActivityPaused();
+        } else if (newState == ActivityState.RESUMED) {
+            onActivityResumed();
+        }
+    }
+
+    @Override
     public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft,
             int oldTop, int oldRight, int oldBottom) {
         keyboardVisibilityPossiblyChanged(UiUtils.isKeyboardShowing(mActivityRef.get(), v));