VR: Don't unregister Daydream intent when leaving webVR page if browsing is supported.

If we support browsing in VR, when we leave a page that support presentation
on headset insertion, don't unregister the Daydream intent.

Bug: 728638
Change-Id: Ie9087e2a2a35a6e5d5839b6f1ef0672ba3b781aa
Reviewed-on: https://chromium-review.googlesource.com/521942Reviewed-by: Yash Malik <ymalik@chromium.org>
Commit-Queue: Michael Thiessen <mthiesse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476459}

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

@@ -936,7 +936,8 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
         // mListeningForWebVrActivate for them.
         if (mVrSupportLevel != VR_DAYDREAM) return;
         mListeningForWebVrActivate = listening;
-        if (listening && !mPaused) {
+        if (mPaused) return;
+        if (listening) {
             registerDaydreamIntent(mVrDaydreamApi, mActivity);
             if (mAutopresentWebVr) {
                 // Dispatch vrdisplayactivate so that the WebVr page can call requestPresent
@@ -946,7 +947,7 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
                 // UI which is suboptimal.
                 nativeDisplayActivate(mNativeVrShellDelegate);
             }
-        } else {
+        } else if (!canEnterVr(mActivity.getActivityTab())) {
             unregisterDaydreamIntent(mVrDaydreamApi);
         }
     }