Expose VSync pausing through WindowAndroid and pause VSync during webVR presentation

chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrWindowAndroid.java

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrWindowAndroid.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrWindowAndroid.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrWindowAndroid.java
index 3eb8b8840d746e6c18e0585cf5cce5d4a8c107ac..5801e2af0f148dc88526a4caeb31665a86c6dd2f 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrWindowAndroid.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrWindowAndroid.java
@@ -15,6 +15,7 @@ import org.chromium.base.ActivityState;
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.base.ApplicationStatus;
 import org.chromium.base.Callback;
+import org.chromium.base.annotations.CalledByNative;
 import org.chromium.ui.base.AndroidPermissionDelegate;
 import org.chromium.ui.base.WindowAndroid;
 import org.chromium.ui.display.DisplayAndroid;
@@ -28,6 +29,8 @@ import java.util.Arrays;
  */
 public class VrWindowAndroid extends WindowAndroid
         implements ApplicationStatus.ActivityStateListener {
+    private boolean mPendingVSync = false;
+    private boolean mWebVRPresenting = false;
 
     public VrWindowAndroid(Context context, DisplayAndroid display) {
         super(context, display);
@@ -74,6 +77,23 @@ public class VrWindowAndroid extends WindowAndroid
         }
     }
 
+    @Override
+    @CalledByNative

[boliu, 2017/03/15 17:15:58]

fwiw, @CalledByNative is used for generating c++ jni headers, meaning it's
totally useless here

+    protected void requestVSyncUpdate() {
+        if (mWebVRPresenting) {
+            mPendingVSync = true;
+            return;
+        }
+        super.requestVSyncUpdate();
+    }
+
+    public void onWebVRPresentationChanged(boolean presenting) {
+        mWebVRPresenting = presenting;
+        setVSyncPaused(mWebVRPresenting);
+
+        if (!mWebVRPresenting && mPendingVSync) super.requestVSyncUpdate();
+    }
+
     // We can't request permissions inside of VR without getting kicked out of VR.
     // TODO(mthiesse): Should we add some UI to ask the user to exit VR, then accept the permission?
     // There's also the possibility that GVR will handle this in the future.