Do not register onLayoutListener unless it is needed

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 59108ce0fefcf6a919892ccbdccebeaa36ef2b55..c83a0cac60cc7f05dac183db393efd6c1663fb36 100644
--- a/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
+++ b/ui/android/java/src/org/chromium/ui/base/ActivityWindowAndroid.java
@@ -51,13 +51,26 @@ public class ActivityWindowAndroid
     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
+    protected void registerKeyboardVisibilityCallbacks() {
+        Activity activity = mActivityRef.get();
+        if (activity == null) return;
+        activity.findViewById(android.R.id.content).addOnLayoutChangeListener(this);

[jdduke (slow), 2015/05/14 21:51:54]

Can this fail on WebView? I guess we shouldn't be calling it on WebView so it's
a natural failure point.

[boliu, 2015/05/14 23:05:29]

Hmm? What do you mean? These were running on webview, and working. I think the
content UI is standard on android, it's like the "root view".

+    }
+
+    @Override
+    protected void unregisterKeyboardVisibilityCallbacks() {
+        Activity activity = mActivityRef.get();
+        if (activity == null) return;
+        activity.findViewById(android.R.id.content).removeOnLayoutChangeListener(this);
+    }
+
+    @Override
     public int showCancelableIntent(
             PendingIntent intent, IntentCallback callback, Integer errorId) {
         Activity activity = mActivityRef.get();