Enable smooth scrolling on mac

content/renderer/render_view_browsertest_mac.mm

 // Copyright (c) 2009 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.
 
 #include "base/string_util.h"
 #include "base/string16.h"
 #include "chrome/test/base/render_view_test.h"
 #include "content/common/native_web_keyboard_event.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 62 matching lines @@
     onkeydown='return OnKeyEvent(event);'>
   <div id='keydown' contenteditable='true'> </div>
   <div id='scroll' contenteditable='true'> </div>
   <p>p1
   <p>p2
   </body>
   </html>
   );
   #undef HTML
 
+  WebPreferences prefs;
+  prefs.enable_scroll_animator = false;
+  view_->OnUpdateWebPreferences(prefs);
+
   const int kMaxOutputCharacters = 1024;
   string16 output;
   char htmlBuffer[2048];
 
   NSEvent* arrowDownKeyDown = CmdDeadKeyEvent(NSKeyDown, kVK_DownArrow);
   NSEvent* arrowUpKeyDown = CmdDeadKeyEvent(NSKeyDown, kVK_UpArrow);
 
   // First test when javascript does not eat keypresses -- should scroll.
   sprintf(htmlBuffer, kRawHtml, "true");
   view_->set_send_content_state_immediately(true);
@@ skipping 37 matching lines @@
   const char* kArrowUpNoScroll =
       "38,false,false,true,false\np1\n\np2";
   view_->OnSetEditCommandsForNextKeyEvent(
       EditCommands(1, EditCommand("moveToBeginningOfDocument", "")));
   SendNativeKeyEvent(NativeWebKeyboardEvent(arrowUpKeyDown));
   ProcessPendingMessages();
   output = GetMainFrame()->contentAsText(kMaxOutputCharacters);
   EXPECT_EQ(kArrowUpNoScroll, UTF16ToASCII(output));
 }