[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 b32cd9b95a81e997d40cc3593ac3871d4a3f1cf8..676e8d6999e4231be757a2f0bdbcdb65e9745ae2 100644
--- a/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
@@ -10,6 +10,9 @@ import android.content.ActivityNotFoundException;
 import android.content.Intent;
 import android.content.IntentSender.SendIntentException;
 
+import org.chromium.base.ActivityState;
+import org.chromium.base.ApplicationStatus;
+
 import java.lang.ref.WeakReference;
 
 /**
@@ -17,7 +20,8 @@ import java.lang.ref.WeakReference;
  * Activity Instance.
  * Only instantiate this class when you need the implemented features.
  */
-public class ActivityWindowAndroid extends WindowAndroid {
+public class ActivityWindowAndroid extends WindowAndroid
+        implements ApplicationStatus.ActivityStateListener {

[no sievers, 2015/03/17 21:37:47]

There is also a native interface in base/android/application_status_listener.cc.
So maybe we don't have to plumb it all the way through java, but could just
register the callback in window_android.cc.

[jdduke (slow), 2015/03/17 22:22:17]

Hmm, I didn't see that, though it looks like that doesn't support per-activity
state listening, e.g., for Hera I don't think it gives us enough fine-grained
listening behavior, as you can't listen to state changes for a single activity.

I could always add that ability, though that might require the native
WindowAndroid knowing about the activity.

     // Constants used for intent request code bounding.
     private static final int REQUEST_CODE_PREFIX = 1000;
     private static final int REQUEST_CODE_RANGE_SIZE = 100;
@@ -29,6 +33,7 @@ public class ActivityWindowAndroid extends WindowAndroid {
     public ActivityWindowAndroid(Activity activity) {
         super(activity.getApplicationContext());
         mActivityRef = new WeakReference<Activity>(activity);
+        ApplicationStatus.registerStateListenerForActivity(this, activity);
     }
 
     @Override
@@ -99,6 +104,14 @@ public class ActivityWindowAndroid extends WindowAndroid {
         return new WeakReference<Activity>(mActivityRef.get());
     }
 
+    @Override
+    public void onActivityStateChange(Activity activity, int newState) {
+        if (newState == ActivityState.PAUSED)
+            onActivityPaused();
+        else if (newState == ActivityState.RESUMED)
+            onActivityResumed();
+    }
+
     private int generateNextRequestCode() {
         int requestCode = REQUEST_CODE_PREFIX + mNextRequestCode;
         mNextRequestCode = (mNextRequestCode + 1) % REQUEST_CODE_RANGE_SIZE;