Reland "Set enable_vr to true on x86/64 Linux"

The revert was caused by some unfortunate timing where a separate
change broke the VR testapp.

This is a reland of 22a43311691cdfbc518dc30c0c12a110fd96e35b
Original change's description:
> Set enable_vr to true on x86/64 Linux
>
> Enables VR on x86/x64 Linux builds. It was decided that instead of
> having a special Linux VR bot that enables ozone and VR on the CQ,
> it was preferrable to enable VR on Linux by default and use the Ozone
> CQ bot.
>
> There should be no performance or functionality impact from this, and
> the binary size impact is reasonable
>
> Bug: 770853
> Change-Id: I3a2add90deb10e7e8f1d9fbee6cf887f01a8bdb9
> Reviewed-on: https://chromium-review.googlesource.com/865955
> Reviewed-by: Christopher Grant <[email protected]>
> Reviewed-by: Bill Orr <[email protected]>
> Reviewed-by: Ian Vollick <[email protected]>
> Commit-Queue: Brian Sheedy <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#529847}

Bug: 770853
Change-Id: I0bba7790b3ec4ead04f0edf3113835c9c551aab7
Reviewed-on: https://chromium-review.googlesource.com/871610
Reviewed-by: agrieve <[email protected]>
Reviewed-by: Christopher Grant <[email protected]>
Reviewed-by: Bill Orr <[email protected]>
Commit-Queue: Brian Sheedy <[email protected]>
Cr-Commit-Position: refs/heads/master@{#530183}
diff --git a/BUILD.gn b/BUILD.gn
index f6cf775..92a85782 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -725,7 +725,7 @@
       "//chrome/browser/vr:vr_common_unittests",
       "//chrome/browser/vr:vr_pixeltests",
     ]
-    if (is_linux && use_ozone) {
+    if (is_desktop_linux && use_ozone) {
       deps += [ "//chrome/browser/vr/testapp:vr_testapp" ]
     }
     if (is_android) {