Enters VrShell if WebVR page doesn not request present in vrdisplayactivate handler.

- Browser goes into VR Browsing Mode when the user inserts the phone into the headeset.
- Browser will then automatically go into presentation mode if page requests present in onvrdisplayactivate handler.
- In a follow-up CL, browser should tentatively go into presentation mode if page is listening for onvrdisplayactivate (and exit presentation if page does not request present).

BUG=703315

Review-Url: https://codereview.chromium.org/2850483003
Cr-Commit-Position: refs/heads/master@{#467714}

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

@@ -420,10 +420,6 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
      */
     private boolean enterVrAfterDon() {
         if (mNativeVrShellDelegate == 0) return false;
-        if (mListeningForWebVrActivateBeforePause && !mRequestedWebVr) {
-            nativeDisplayActivate(mNativeVrShellDelegate);
-            return true;
-        }
 
         // Normally, if the active page doesn't have a vrdisplayactivate listener, and WebVR was not
         // presenting and VrShell was not enabled, the Daydream Homescreen should show after the DON
@@ -434,6 +430,10 @@ public class VrShellDelegate implements ApplicationStatus.ActivityStateListener,
             return false;
         }
 
+        if (mListeningForWebVrActivateBeforePause && !mRequestedWebVr) {
+            nativeDisplayActivate(mNativeVrShellDelegate);
+        }
+
         enterVr();
         return true;
     }