Linux/CrOS smooth scrolling support - behind a flag.

chrome/chrome_browser.gypi

 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'msvs_guid': '5BF908A7-68FB-4A4B-99E3-8C749F1FE4EA',
@@ skipping 4440 matching lines @@
         ['file_manager_extension==1', {
           'sources/': [
             ['exclude', '^browser/ui/gtk/dialogs_gtk.cc'],
             ['exclude', '^browser/ui/views/select_file_dialog.cc'],
             ['include', '^browser/ui/views/file_manager_dialogs.cc'],
           ]}, {
           'sources/': [
             ['exclude', '^browser/ui/views/file_manager_dialogs.cc'],
           ]}
         ],
+        ['OS=="linux" and enable_smooth_scrolling==1', {
+          'defines': [
+            'ENABLE_SMOOTH_SCROLLING',
+          ],
+        }],
       ],
     },
     {
       # Protobuf compiler / generate rule for feedback
       'target_name': 'userfeedback_proto',
       'type': 'none',
       'sources': [
         'browser/userfeedback/proto/annotations.proto',
         'browser/userfeedback/proto/chrome.proto',
         'browser/userfeedback/proto/common.proto',
@@ skipping 151 matching lines @@
       'hard_dependency': 1,
     },
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: