Fix disk read violation when create GvrLayout

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

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
index d391c762ba044d380f410f36ddd759b7c169cc92..a247b1f56d7fdb8d73dd3fa1e6ec46b60054e967 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrShellDelegate.java
@@ -409,6 +409,7 @@ public class VrShellDelegate {
     private long createNonPresentingNativeContext() {
         if (mVrClassesBuilder == null) return 0;
         mNonPresentingGvrContext = mVrClassesBuilder.createNonPresentingGvrContext();
+        if (mNonPresentingGvrContext == null) return 0;
         return mNonPresentingGvrContext.getNativeGvrContext();
     }
 
@@ -472,11 +473,8 @@ public class VrShellDelegate {
 
     private boolean createVrShell() {
         if (mVrClassesBuilder == null) return false;
-        StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
-        StrictMode.allowThreadDiskWrites();
         mVrShell = mVrClassesBuilder.createVrShell();
-        StrictMode.setThreadPolicy(oldPolicy);
-        return true;
+        return mVrShell != null;
     }
 
     private void addVrViews() {