Enable smooth scrolling on mac

chrome/browser/tab_contents/render_view_host_delegate_helper.cc

 // 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.
 
 #include "chrome/browser/tab_contents/render_view_host_delegate_helper.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/string_util.h"
@@ skipping 442 matching lines @@
     web_prefs.memory_info_enabled =
         command_line.HasSwitch(switches::kEnableMemoryInfo);
     web_prefs.interactive_form_validation_enabled =
         !command_line.HasSwitch(switches::kDisableInteractiveFormValidation);
     web_prefs.fullscreen_enabled =
         command_line.HasSwitch(switches::kEnableFullScreen);
     web_prefs.allow_displaying_insecure_content =
         prefs->GetBoolean(prefs::kWebKitAllowDisplayingInsecureContent);
     web_prefs.allow_running_insecure_content =
         prefs->GetBoolean(prefs::kWebKitAllowRunningInsecureContent);
-    web_prefs.enable_scroll_animator =
-        command_line.HasSwitch(switches::kEnableSmoothScrolling);
+
+#if defined(OS_MACOSX)
+    bool default_enable_scroll_animator = true;
+#else
+    // On CrOS, the launcher always passes in the --enable flag.
+    bool default_enable_scroll_animator = false;
+#endif
+    web_prefs.enable_scroll_animator = default_enable_scroll_animator;
+    if (command_line.HasSwitch(switches::kEnableSmoothScrolling))
+      web_prefs.enable_scroll_animator = true;
+#if defined(OS_MACOSX)
+    if (command_line.HasSwitch(switches::kDisableMacSmoothScrollingForTesting))
+      web_prefs.enable_scroll_animator = false;
+#endif
 
     // The user stylesheet watcher may not exist in a testing profile.
     if (profile->GetUserStyleSheetWatcher()) {
       web_prefs.user_style_sheet_enabled = true;
       web_prefs.user_style_sheet_location =
           profile->GetUserStyleSheetWatcher()->user_style_sheet();
     } else {
       web_prefs.user_style_sheet_enabled = false;
     }
   }
@@ skipping 47 matching lines @@
   DictionaryValue* inspector_settings = update.Get();
   inspector_settings->SetWithoutPathExpansion(key,
                                               Value::CreateStringValue(value));
 }
 
 void RenderViewHostDelegateHelper::ClearInspectorSettings(
     content::BrowserContext* browser_context) {
   Profile::FromBrowserContext(browser_context)->GetPrefs()->
       ClearPref(prefs::kWebKitInspectorSettings);
 }