Fix handling of navigation to external app

Previously, we want all redirection stays in Chrome while in VR. The problem is
if a webpage sends a redirection request that Chrome can't navigate to
(i.e. intent://*). Chrome just silently block the request. This leads to problem
described in issue 848788.
This CL unblocks such redirection (when redirect to an external app).

Bug: 848788
Change-Id: Ia1fc66afe1d011d1c814f7a907d423f053e7fb28
Reviewed-on: https://chromium-review.googlesource.com/1087775Reviewed-by: Michael Thiessen <mthiesse@chromium.org>
Commit-Queue: Biao She <bshe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564889}

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

@@ -189,7 +189,7 @@ public class VrShellImpl
         mTabRedirectHandler = new TabRedirectHandler(mActivity) {
             @Override
             public boolean shouldStayInChrome(boolean hasExternalProtocol) {
-                return true;
+                return !hasExternalProtocol;
             }
         };