VR: Turn VR mode off when restoring Activity from saved instance.

When Chrome is killed in the background while VR mode is on, we can't
turn VR mode off (the platform doesn't respect VR mode changes for
backgrounded apps).

We also can't check whether VR mode is currently on on Android N, so
instead this CL records whether we were in VR mode when killed using
saved instance state, and turns VR mode off on startup when restoring.

Test/Repro steps:
1. Turn on "Don't keep activities" in developer settings
2. Launch Chrome in VR
3. Press the Daydream controller Home button
4. Exit VR
5. Use task switcher to return to Chrome.

> Chrome should resume without VR mode on (the display will flicker
if it's on)

Bug: 854740
Change-Id: I4fc8e9c076a8cb31ca2bdb74be1124bec3826193
Reviewed-on: https://chromium-review.googlesource.com/1167116
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581957}

chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java

@@ -318,11 +318,7 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
     public void preInflationStartup() {
         super.preInflationStartup();
 
-        // We need to explicitly enable VR mode here so that the system doesn't kick us out of VR,
-        // or drop us into the 2D-in-VR rendering mode, while we prepare for VR rendering.
-        if (VrModuleProvider.getIntentDelegate().isLaunchingIntoVr(this, getIntent())) {
-            VrModuleProvider.getDelegate().setVrModeEnabled(this, true);
-        }
+        VrModuleProvider.getDelegate().doPreInflationStartup(this, getSavedInstanceState());
 
         // Force a partner customizations refresh if it has yet to be initialized.  This can happen
         // if Chrome is killed and you refocus a previous activity from Android recents, which does
@@ -1196,6 +1192,12 @@ public abstract class ChromeActivity extends AsyncInitializationActivity
         return super.getOnCreateTimestampMs();
     }
 
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+        VrModuleProvider.getDelegate().onSaveInstanceState(outState);
+    }
+
     /**
      * This cannot be overridden in order to preserve destruction order.  Override
      * {@link #onDestroyInternal()} instead to perform clean up tasks.

chrome/android/java/src/org/chromium/chrome/browser/vr/VrDelegate.java

@@ -6,6 +6,7 @@ package org.chromium.chrome.browser.vr;
 
 import android.app.Activity;
 import android.content.Intent;
+import android.os.Bundle;
 
 import org.chromium.chrome.browser.ChromeActivity;
 
@@ -34,8 +35,10 @@ public interface VrDelegate {
     void onNewIntentWithNative(ChromeActivity activity, Intent intent);
     void maybeHandleVrIntentPreNative(ChromeActivity activity, Intent intent);
     void setVrModeEnabled(Activity activity, boolean enabled);
+    void doPreInflationStartup(ChromeActivity activity, Bundle savedInstanceState);
     boolean bootsToVr();
     boolean isDaydreamReadyDevice();
     boolean isDaydreamCurrentViewer();
     boolean willChangeDensityInVr(ChromeActivity activity);
+    void onSaveInstanceState(Bundle outState);
 }

chrome/android/java/src/org/chromium/chrome/browser/vr/VrDelegateFallback.java

@@ -107,6 +107,9 @@ import org.chromium.chrome.browser.ChromeActivity;
         assert false;
     }
 
+    @Override
+    public void doPreInflationStartup(ChromeActivity activity, Bundle savedInstanceState) {}
+
     @Override
     public boolean bootsToVr() {
         return false;
@@ -149,4 +152,7 @@ import org.chromium.chrome.browser.ChromeActivity;
         assert false;
         return false;
     }
+
+    @Override
+    public void onSaveInstanceState(Bundle outState) {}
 }

chrome/android/java/src/org/chromium/chrome/browser/vr/VrDelegateImpl.java

@@ -128,6 +128,11 @@ import org.chromium.chrome.browser.ChromeActivity;
         VrShellDelegate.setVrModeEnabled(activity, enabled);
     }
 
+    @Override
+    public void doPreInflationStartup(ChromeActivity activity, Bundle savedInstanceState) {
+        VrShellDelegate.doPreInflationStartup(activity, savedInstanceState);
+    }
+
     @Override
     public boolean bootsToVr() {
         return VrShellDelegate.bootsToVr();
@@ -167,4 +172,9 @@ import org.chromium.chrome.browser.ChromeActivity;
     public boolean willChangeDensityInVr(ChromeActivity activity) {
         return VrShellDelegate.willChangeDensityInVr(activity);
     }
+
+    @Override
+    public void onSaveInstanceState(Bundle outState) {
+        VrShellDelegate.onSaveInstanceState(outState);
+    }
 }

chrome/android/java/src/org/chromium/chrome/browser/vr/VrShellDelegate.java

@@ -144,6 +144,9 @@ public class VrShellDelegate
 
     private static final String VR_BOOT_SYSTEM_PROPERTY = "ro.boot.vr";
 
+    /** ID for SavedInstanceState Bundle for whether Chrome was in VR when killed. */
+    private static final String IN_VR = "in_vr";
+
     private static VrShellDelegate sInstance;
     private static VrBroadcastReceiver sVrBroadcastReceiver;
     private static VrLifecycleObserver sVrLifecycleObserver;
@@ -664,6 +667,30 @@ public class VrShellDelegate
         }
     }
 
+    /**
+     * Performs pre-inflation VR-related startup.
+     */
+    public static void doPreInflationStartup(ChromeActivity activity, Bundle savedInstanceState) {
+        // We need to explicitly enable VR mode here so that the system doesn't kick us out of VR,
+        // or drop us into the 2D-in-VR rendering mode, while we prepare for VR rendering.
+        if (VrIntentUtils.isLaunchingIntoVr(activity, activity.getIntent())) {
+            setVrModeEnabled(activity, true);
+        } else if (savedInstanceState != null && savedInstanceState.getBoolean(IN_VR, false)) {
+            // When Chrome is restored from a SavedInstanceState with VR mode still on we need to
+            // Explicitly turn VR mode off even though we can't really know for sure whether or not
+            // it's currently on.
+            AndroidCompat.setVrModeEnabled(activity, false);
+            sVrModeEnabledActivitys.remove(activity);
+        }
+    }
+
+    /**
+     * See {@link Activity#onSaveInstanceState(Bundle)}
+     */
+    public static void onSaveInstanceState(Bundle outState) {
+        if (isInVr()) outState.putBoolean(IN_VR, true);
+    }
+
     /**
      * See VrClassesWrapper#bootsToVr().
      */