Adding Chrome-side WebVR interface

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

+// 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.CalledByNative;
+import org.chromium.base.JNINamespace;
+
+/**
+ * This is the implementation of the C++ counterpart CardboardVRDevice.
+ */
+@JNINamespace("content")
+class CardboardVRDevice {
+    private static final String TAG = "CardboardVRDevice";
+    private HeadMountedDisplayManager mHMDManager;
+    private HeadTracker mHeadTracker;
+    private long mVrDevicePtr;
+
+    @CalledByNative
+    private static CardboardVRDevice create(Context context, long vrDevicePtr) {
+        return new CardboardVRDevice(context, vrDevicePtr);
+    }
+
+    private CardboardVRDevice(Context context, long vrDevicePtr) {
+        mVrDevicePtr = vrDevicePtr;
+
+        mHMDManager = new HeadMountedDisplayManager(context);

[Ted C, 2015/03/28 00:56:04]

Should we be calling things like this:
https://developers.google.com/cardboard/android/latest/reference/com/google/v...

Are we wasting battery if we don't?

And I tried digging through parts of this change and I never see how we actually
determine if a cardboard device is actually available.

What happens if it becomes unavailable?  I don't see anything in the API that
signals that nor do I see handling.

To me, this logic doesn't mimic any of the other external device APIs were you
have to handle devices appearing and disappearing, so I feel like I'm missing
something.

+
+        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() {

[Ted C, 2015/03/28 00:56:04]

java says to not capitalize acronyms

https://source.android.com/source/code-style.html#treat-acronyms-as-words  

+        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();
+    }
+}