Rename build flag from enable_webvr to enable_vr

This makes the build flag better represent what it's actually doing.
More specific flags will be added as needed.

BUG=None
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation
[email protected]

Review-Url: https://codereview.chromium.org/2763073002
Cr-Commit-Position: refs/heads/master@{#458540}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 6c620cb..99b8407 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -3541,7 +3541,7 @@
     ]
   }
 
-  if (enable_webvr) {
+  if (enable_vr) {
     if (is_android) {
       deps += [ "android/vr_shell:vr_common" ]
       configs += [ "//third_party/gvr-android-sdk:libgvr_config" ]