[Temp] Make |enable_webvr==0| work.

**IMPORTANT**
We actually intend to fix this properly. We are cherry-picking this
commit from the crosswalk-18 branch first in order to have a stable
baseline with no WebVR support propagating from Crosswalk 21 to 20 to
19. After that, we can start working on fixing this in 21 and 20 and, if
there is enough time, 19 too.

*From the original commit message:*

Move `CardboardVRDevice.java` to a different directory so that it is not
built by the `content_java` target even if `enable_webvr==0`.

This is a prerequisite for getting the code to build with
`enable_webvr=0`.

BUG=XWALK-6746

(cherry picked from commit e593418)

M53 rebasing notes: added GN support:

> [Temp] Make |enable_webvr==false| work in GN.
>
> This is a change that should be squashed into "[Temp] Make
> |enable_webvr==0| work", and just adds the required changes to the GN
> build so that it is aware of the fact that CardboardVRDevice.java
> resides in another directory.
>
> BUG=XWALK-6746

content/content.gyp

@@ -546,6 +546,11 @@
             'has_java_resources': 1,
             'R_package': 'org.chromium.content',
             'R_package_relpath': 'org/chromium/content',
+            'conditions': [
+               ['enable_webvr==1', {
+                 'additional_src_dirs': ['../content/public/android/java-optional'],
+               }],
+             ],
           },
           'includes': [ '../build/java.gypi' ],
         },
@@ -692,7 +697,7 @@
           'conditions': [
             ['enable_webvr==1', {
               'sources': [
-                'public/android/java/src/org/chromium/content/browser/input/CardboardVRDevice.java',
+                'public/android/java-optional/src/org/chromium/content/browser/input/CardboardVRDevice.java',
               ],
               'dependencies': [
                 '../third_party/cardboard-java/cardboard.gyp:cardboard_jar',

content/public/android/BUILD.gn

@@ -206,6 +206,11 @@ android_library("content_java") {
     "java/src/org/chromium/content_public/common/ResourceRequestBody.java",
     "java/src/org/chromium/content_public/common/ScreenOrientationConstants.java",
   ]
+
+  if (enable_webvr) {
+    deps += [ "//third_party/cardboard-java:cardboard-java" ]
+    java_files += [ "java-optional/src/org/chromium/content/browser/input/CardboardVRDevice.java" ]
+  }
 }
 
 java_strings_grd("content_strings_grd") {
@@ -286,6 +291,13 @@ generate_jar_jni("jar_jni") {
 generate_jni("content_jni_headers") {
   sources = rebase_path(content_jni_gypi_values.sources, "", "../..")
   jni_package = "content"
+
+  if (enable_webvr) {
+    sources += [ "//content/public/android/java-optional/src/org/chromium/content/browser/input/CardboardVRDevice.java" ]
+    public_deps = [
+      "//third_party/cardboard-java:cardboard-java",
+    ]
+  }
 }
 
 group("jni") {

content/public/android/java-optional/src/org/chromium/content/browser/input/CardboardVRDevice.java

@@ -0,0 +1,88 @@
+// Copyright 2015 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.content.browser.input;
+
+import android.content.Context;
+
+import com.google.vrtoolkit.cardboard.CardboardDeviceParams;
+import com.google.vrtoolkit.cardboard.FieldOfView;
+import com.google.vrtoolkit.cardboard.HeadMountedDisplay;
+import com.google.vrtoolkit.cardboard.HeadMountedDisplayManager;
+import com.google.vrtoolkit.cardboard.ScreenParams;
+import com.google.vrtoolkit.cardboard.sensors.HeadTracker;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+/**
+ * This is the implementation of the C++ counterpart CardboardVRDevice.
+ */
+@JNINamespace("content")
+class CardboardVRDevice {
+    private static final String TAG = "CardboardVRDevice";
+    private final HeadMountedDisplayManager mHMDManager;
+    private final HeadTracker mHeadTracker;
+
+    @CalledByNative
+    private static CardboardVRDevice create(Context context) {
+        return new CardboardVRDevice(context);
+    }
+
+    private CardboardVRDevice(Context context) {
+        mHMDManager = new HeadMountedDisplayManager(context);
+
+        mHeadTracker = HeadTracker.createFromContext(context);
+        mHeadTracker.setNeckModelEnabled(true);
+        mHeadTracker.startTracking();
+    }
+
+    @CalledByNative
+    private void getFieldOfView(float[] outFov) {
+        HeadMountedDisplay hmd = mHMDManager.getHeadMountedDisplay();
+        CardboardDeviceParams deviceParams = hmd.getCardboardDeviceParams();
+        FieldOfView fov = deviceParams.getLeftEyeMaxFov();
+        outFov[0] = fov.getTop();
+        outFov[1] = fov.getBottom();
+        outFov[2] = fov.getLeft();
+        outFov[3] = fov.getRight();
+    }
+
+    @CalledByNative
+    private float getIpd() {
+        HeadMountedDisplay hmd = mHMDManager.getHeadMountedDisplay();
+        CardboardDeviceParams deviceParams = hmd.getCardboardDeviceParams();
+        return deviceParams.getInterLensDistance();
+    }
+
+    @CalledByNative
+    private String getDeviceName() {
+        HeadMountedDisplay hmd = mHMDManager.getHeadMountedDisplay();
+        CardboardDeviceParams deviceParams = hmd.getCardboardDeviceParams();
+        return deviceParams.getVendor() + " " + deviceParams.getModel();
+    }
+
+    @CalledByNative
+    private void getScreenSize(int[] outSize) {
+        HeadMountedDisplay hmd = mHMDManager.getHeadMountedDisplay();
+        ScreenParams screenParams = hmd.getScreenParams();
+        outSize[0] = screenParams.getWidth();
+        outSize[1] = screenParams.getHeight();
+    }
+
+    @CalledByNative
+    private void getSensorState(float[] outMatrix) {
+        mHeadTracker.getLastHeadView(outMatrix, 0);
+    }
+
+    @CalledByNative
+    private void stopTracking() {
+        mHeadTracker.stopTracking();
+    }
+
+    @CalledByNative
+    private void resetSensor() {
+        mHeadTracker.resetTracker();
+    }
+}