Support "display": "fullscreen" for sites added to the home screen.

chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java
index 901b62b51f70f11bef575b192284684282548dd1..9d1054d7bd50ddcabb070bcadac20d210071cbba 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/FullScreenActivity.java
@@ -5,8 +5,10 @@
 package org.chromium.chrome.browser.webapps;
 
 import android.content.Intent;
+import android.os.Build;
 import android.util.Pair;
 import android.view.View;
+import android.view.View.OnSystemUiVisibilityChangeListener;
 import android.view.ViewGroup;
 
 import org.chromium.base.annotations.SuppressFBWarnings;
@@ -46,6 +48,20 @@ public abstract class FullScreenActivity extends ChromeActivity {
     protected static final String BUNDLE_TAB_URL = "tabUrl";
     private static final String TAG = "FullScreenActivity";
 
+    private static final int ENTER_IMMERSIVE_MODE_DELAY_MILLIS = 300;
+    private static final int RESTORE_IMMERSIVE_MODE_DELAY_MILLIS = 3000;
+    private static final int IMMERSIVE_MODE_UI_FLAGS =
+            View.SYSTEM_UI_FLAG_LAYOUT_STABLE
+                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
+                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
+                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION // hide nav bar
+                | View.SYSTEM_UI_FLAG_FULLSCREEN // hide status bar
+                | View.SYSTEM_UI_FLAG_LOW_PROFILE
+                | View.SYSTEM_UI_FLAG_IMMERSIVE;
+
+    private boolean mEnteredImmersive;
+    private Runnable mSetImmersiveRunnable;
+
     private Tab mTab;
 
     private WebContents mWebContents;
@@ -179,6 +195,62 @@ public abstract class FullScreenActivity extends ChromeActivity {
         };
     }
 
+    @Override
+    public void onWindowFocusChanged(boolean hasFocus) {
+        super.onWindowFocusChanged(hasFocus);
+
+        if (hasFocus && (mSetImmersiveRunnable != null)) {
+            enterImmersiveMode(getWindow().getDecorView());
+        }
+    }
+
+    /**
+     * Ensure the given {@link View} is in fullscreen immersion if this device supports.
+     */
+    protected void enterImmersiveMode(final View decor) {
+        if (!supportsImmersiveMode()) {

[dominickn, 2017/01/18 05:56:17]

Minor nit: the style guide lets you do this for short conditionals:

if (!supportsImmersiveMode()) return;

[Leo, 2017/01/18 23:03:12]

Done.

+            return;
+        }
+
+        if (mSetImmersiveRunnable == null) {
+            mSetImmersiveRunnable = new Runnable() {
+                @Override
+                public void run() {
+                    int currentFlags = decor.getSystemUiVisibility();
+                    int desiredFlags = currentFlags | IMMERSIVE_MODE_UI_FLAGS;
+                    if (currentFlags != desiredFlags) {
+                        decor.setSystemUiVisibility(desiredFlags);
+                    }
+                }
+            };
+        }
+
+        // When we enter immersive mode for the first time, register a
+        // SystemUiVisibilityChangeListener that restores immersive mode. This is necessary
+        // because user actions like focusing a keyboard will break out of immersive.
+        if (!mEnteredImmersive) {
+            decor.setOnSystemUiVisibilityChangeListener(new OnSystemUiVisibilityChangeListener() {
+                @Override
+                public void onSystemUiVisibilityChange(int newFlags) {
+                    if ((newFlags & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
+                        asyncSetImmersive(decor, RESTORE_IMMERSIVE_MODE_DELAY_MILLIS);
+                    }
+                }
+            });
+        }
+        // Set immersive mode asynchronously.

[dominickn, 2017/01/18 05:56:17]

Minor nit: you can probably remove this comment because it just repeats the
method name.

[Leo, 2017/01/18 23:03:12]

Done.

+        asyncSetImmersive(decor, ENTER_IMMERSIVE_MODE_DELAY_MILLIS);
+        mEnteredImmersive = true;
+    }
+
+    private void asyncSetImmersive(final View decor, int delayInMills) {
+        if (mSetImmersiveRunnable == null) {

[dominickn, 2017/01/18 05:56:17]

Minor style nit: you can inline the return here.

[Leo, 2017/01/18 23:03:12]

Done. And remove unused decor.

+            return;
+        }
+        mHandler.removeCallbacks(mSetImmersiveRunnable);
+        mHandler.postDelayed(mSetImmersiveRunnable, delayInMills);
+    }
+
     /**
      * @return {@link TabDelegateFactory} to be used while creating the associated {@link Tab}.
      */
@@ -206,4 +278,11 @@ public abstract class FullScreenActivity extends ChromeActivity {
     @Override
     public void onCheckForUpdate(boolean updateAvailable) {
     }
+
+    /**
+     ** @return true if this device supports immersive mode functionality.

[dominickn, 2017/01/18 05:56:17]

Minor style nit: single * after the first line of the comment.

/**
 * @return etc.
 */

[Leo, 2017/01/18 23:03:12]

Thanks for the correction. I found this method is only called once, so merged
code into where it was used.

+     **/
+    public static boolean supportsImmersiveMode() {
+        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;
+    }
 }