Remove defunct chromeos_gtk gyp variable.

build/all.gyp

Index: build/all.gyp
diff --git a/build/all.gyp b/build/all.gyp
index 823a739c8cb90468a8f224db3c7257cba0e1b51c..731b28c158d35caeab275856d716b73c64fc8d95 100644
--- a/build/all.gyp
+++ b/build/all.gyp
@@ -542,44 +542,6 @@
         }], # branding=="Chrome"
        ], # conditions
     }], # OS="win"
-    # Old ChromeOS target needed to build pre-Aura targets.
-    ['chromeos_gtk==1', {
-      'targets': [
-        {
-          'target_name': 'chromeos_builder',
-          'type': 'none',
-          'dependencies': [
-            '../base/base.gyp:base_unittests',
-            '../chrome/chrome.gyp:browser_tests',
-            '../chrome/chrome.gyp:chrome',
-            '../chrome/chrome.gyp:interactive_ui_tests',
-            '../chrome/chrome.gyp:performance_browser_tests',
-            '../chrome/chrome.gyp:performance_ui_tests',
-            '../chrome/chrome.gyp:safe_browsing_tests',
-            '../chrome/chrome.gyp:sync_integration_tests',
-            '../chrome/chrome.gyp:sync_unit_tests',
-            '../chrome/chrome.gyp:ui_tests',
-            '../chrome/chrome.gyp:unit_tests',
-            '../content/content.gyp:content_unittests',
-            '../crypto/crypto.gyp:crypto_unittests',
-            '../dbus/dbus.gyp:dbus_unittests',
-            '../ipc/ipc.gyp:ipc_tests',
-            '../jingle/jingle.gyp:jingle_unittests',
-            '../media/media.gyp:ffmpeg_tests',
-            '../media/media.gyp:media_unittests',
-            '../net/net.gyp:net_unittests',
-            '../printing/printing.gyp:printing_unittests',
-            '../remoting/remoting.gyp:remoting_unittests',
-            '../sql/sql.gyp:sql_unittests',
-            '../third_party/cacheinvalidation/cacheinvalidation.gyp:cacheinvalidation_unittests',
-            '../third_party/libphonenumber/libphonenumber.gyp:libphonenumber_unittests',
-            '../ui/ui.gyp:gfx_unittests',
-            '../ui/views/views.gyp:views_unittests',
-            'temp_gyp/googleurl.gyp:googleurl_unittests',
-          ],
-        },
-      ], # targets
-    }], # "chromeos_gtk==1"
     ['use_aura==1', {
       'targets': [
         {