On Linux, pick the color of the slider's thumbpart from the GTK theme....

chrome/browser/tab_contents/tab_contents.cc

 // 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 "chrome/browser/tab_contents/tab_contents.h"
 
 #include "app/gfx/text_elider.h"
 #include "app/l10n_util.h"
 #include "app/resource_bundle.h"
 #include "base/file_version_info.h"
@@ skipping 241 matching lines @@
       capturing_contents_(false),
       is_being_destroyed_(false),
       notify_disconnection_(false),
       history_requests_(),
 #if defined(OS_WIN)
       message_box_active_(CreateEvent(NULL, TRUE, FALSE, NULL)),
 #endif
       last_javascript_message_dismissal_(),
       suppress_javascript_messages_(false),
       is_showing_before_unload_dialog_(false),
-      renderer_preferences_(platform_util::GetInitedRendererPreferences()),
+      renderer_preferences_(
+        platform_util::GetInitedRendererPreferences(profile)),
       opener_dom_ui_type_(DOMUIFactory::kNoDOMUI) {
 #if defined(OS_CHROMEOS)
   // Make sure the thumbnailer is started before starting the render manager.
   // The thumbnailer will want to listen for RVH creations, one of which will
   // happen in RVHManager::Init.
   ThumbnailGenerator* generator = g_browser_process->GetThumbnailGenerator();
   if (generator)
     generator->StartThumbnailing();
 #endif
 
@@ skipping 1602 matching lines @@
     form_field_history_manager_.reset(new FormFieldHistoryManager(this));
   return form_field_history_manager_.get();
 }
 
 RenderViewHostDelegate::AutoFill* TabContents::GetAutoFillDelegate() {
   if (autofill_manager_.get() == NULL)
     autofill_manager_.reset(new AutoFillManager(this));
   return autofill_manager_.get();
 }
 
-RendererPreferences TabContents::GetRendererPrefs() const {
+RendererPreferences TabContents::GetRendererPrefs(Profile* profile) const {
   return renderer_preferences_;
 }
 
 TabContents* TabContents::GetAsTabContents() {
   return this;
 }
 
 void TabContents::AddBlockedNotice(const GURL& url, const string16& reason) {
   CreateBlockedPopupContainerIfNecessary();
   blocked_popups_->AddBlockedNotice(url, reason);
@@ skipping 742 matching lines @@
   render_view_host()->JavaScriptMessageBoxClosed(reply_msg, success, prompt);
 }
 
 void TabContents::SetSuppressMessageBoxes(bool suppress_message_boxes) {
   set_suppress_javascript_messages(suppress_message_boxes);
 }
 
 void TabContents::set_encoding(const std::string& encoding) {
   encoding_ = CharacterEncoding::GetCanonicalEncodingNameByAliasName(encoding);
 }