Remove ENABLE_VR_SHELL compile-time define.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 31f3104c6251aa6187dc9b1878cf25621641bfe1..254036b9a53e3aadfa66ff4c536e58d5179cfe8f 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1598,11 +1598,9 @@ const FeatureEntry kFeatureEntries[] = {
 #endif  // OS_MACOSX
     {"enable-webvr", IDS_FLAGS_WEBVR_NAME, IDS_FLAGS_WEBVR_DESCRIPTION, kOsAll,
      SINGLE_VALUE_TYPE(switches::kEnableWebVR)},
-#if defined(ENABLE_VR_SHELL)

[amp, 2017/02/07 19:26:01]

We only want this to show up on platforms that can support vr.  If we are
getting rid of the vr shell build flag, we should wrap this in the web vr build
flag.

[mthiesse, 2017/02/07 19:33:26]

+1, I think this is the only useful use of ENABLE_VR_SHELL currently. The rest
of the changes seem like the right thing to me.

[cjgrant, 2017/02/07 20:10:17]

It's interesting though that the "enable-webvr" flag above isn't wrapped in a
WebVR build flag.  By this logic, should it not be?

[amp, 2017/02/07 20:23:10]

Maybe it should be.  I think I had that same question when I added this build
check, but platform features are odd though (because they just add an API, not
new experiences like VrShell would).

I'll defer to the about flags OWNER review to make that call.  It is possible to
turn the flag on for any platform, even if it doesn't show up in about://flags,
so maybe it doesn't make a big difference either way.

     {"enable-vr-shell", IDS_FLAGS_ENABLE_VR_SHELL_NAME,
      IDS_FLAGS_ENABLE_VR_SHELL_DESCRIPTION, kOsAndroid,
      FEATURE_VALUE_TYPE(features::kVrShell)},
-#endif  // ENABLE_VR_SHELL
 #if defined(OS_CHROMEOS)
     {"disable-accelerated-mjpeg-decode",
      IDS_FLAGS_ACCELERATED_MJPEG_DECODE_NAME,