Use VrClassesBuilder to reduce reflection usage

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

Index: chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrClassesBuilder.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrClassesBuilder.java b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrClassesBuilder.java
new file mode 100644
index 0000000000000000000000000000000000000000..a2c4de721f9c9578fd99c4c1a5fa73448ecdd9eb
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/vr_shell/VrClassesBuilder.java
@@ -0,0 +1,31 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.vr_shell;
+
+/**
+ * Abstracts away the VrClassesBuilderImpl class, which may or may not be present at runtime
+ * depending on compile flags.
+ */
+public interface VrClassesBuilder {
+    /**
+     * Creates a NonPresentingGvrContextImpl instance.
+     */
+    public NonPresentingGvrContext createNonPresentingGvrContext();
+
+    /**
+     * Creates a VrShellImpl instance.
+     */
+    public VrShell createVrShell();
+
+    /**
+     * Creates a VrDaydreamApImpl instance.
+     */
+    public VrDaydreamApi createVrDaydreamApi();
+
+    /**
+    * Creates a VrCoreVersionCheckerImpl instance.
+    */
+    public VrCoreVersionChecker createVrCoreVersionChecker();
+}