play fullscreen video in immersive mode

content/public/android/java/src/org/chromium/content/browser/ActivityContentVideoViewClient.java

Index: content/public/android/java/src/org/chromium/content/browser/ActivityContentVideoViewClient.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/ActivityContentVideoViewClient.java b/content/public/android/java/src/org/chromium/content/browser/ActivityContentVideoViewClient.java
index 6acf8dca57046e5d142c90f2a54b58125e90d8ab..292993229b8ba8ba9e7b845c667914da770216a5 100644
--- a/content/public/android/java/src/org/chromium/content/browser/ActivityContentVideoViewClient.java
+++ b/content/public/android/java/src/org/chromium/content/browser/ActivityContentVideoViewClient.java
@@ -5,6 +5,7 @@
 package org.chromium.content.browser;
 
 import android.app.Activity;
+import android.os.Build;
 import android.view.Gravity;
 import android.view.View;
 import android.view.ViewGroup;
@@ -24,24 +25,22 @@ public class ActivityContentVideoViewClient implements ContentVideoViewClient {
 
     @Override
     public boolean onShowCustomView(View view) {
-        mActivity.getWindow().setFlags(
-                WindowManager.LayoutParams.FLAG_FULLSCREEN,
-                WindowManager.LayoutParams.FLAG_FULLSCREEN);
-
-        mActivity.getWindow().addContentView(view,
-                new FrameLayout.LayoutParams(
-                        ViewGroup.LayoutParams.MATCH_PARENT,
-                        ViewGroup.LayoutParams.MATCH_PARENT,
-                        Gravity.CENTER));
+        FrameLayout decor = (FrameLayout) mActivity.getWindow().getDecorView();
+        decor.addView(view, 0,
+            new FrameLayout.LayoutParams(
+                    ViewGroup.LayoutParams.MATCH_PARENT,
+                    ViewGroup.LayoutParams.MATCH_PARENT,
+                    Gravity.CENTER));
+        setSystemUiVisibility(decor, true);
         mView = view;
         return true;
     }
 
     @Override
     public void onDestroyContentVideoView() {
-        mActivity.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
         FrameLayout decor = (FrameLayout) mActivity.getWindow().getDecorView();
         decor.removeView(mView);
+        setSystemUiVisibility(decor, false);
         mView = null;
     }
 
@@ -49,4 +48,35 @@ public class ActivityContentVideoViewClient implements ContentVideoViewClient {
     public View getVideoLoadingProgressView() {
         return null;
     }
+
+    /**
+     * Returns the system ui visibility after entering or exiting fullscreen.
+     * @param view The decor view belongs to the activity window
+     * @param enterFullscreen True if video is going fullscreen, or false otherwise.
+     */
+    private void setSystemUiVisibility(View view, boolean enterFullscreen) {
+        if (enterFullscreen) {
+            mActivity.getWindow().setFlags(
+                WindowManager.LayoutParams.FLAG_FULLSCREEN,
+                WindowManager.LayoutParams.FLAG_FULLSCREEN);
+        } else {
+            mActivity.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
+        }
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
+            return;
+        }
+
+        int systemUiVisibility = view.getSystemUiVisibility();
+        int flags = View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
+                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
+                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
+                | View.SYSTEM_UI_FLAG_FULLSCREEN
+                | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
+        if (enterFullscreen) {
+            systemUiVisibility |= flags;
+        } else {
+            systemUiVisibility &= ~flags;
+        }
+        view.setSystemUiVisibility(systemUiVisibility);
+    }
 }