GTK: Use GTK+ theme selection colors and plumb them into webkit.

chrome/common/renderer_preferences.h

 // Copyright (c) 2006-2008 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.
 //
 // A struct for managing browser's settings that apply to the renderer or its
 // webview.  These differ from WebPreferences since they apply to Chromium's
 // glue layer rather than applying to just WebKit.
 //
 // Adding new values to this class probably involves updating
 // common/render_messages.h, browser/browser.cc, etc.
@@ skipping 39 matching lines @@
 
   // The color of the focus ring. Currently only used on Linux.
   SkColor focus_ring_color;
 
   // The color of different parts of the scrollbar. Currently only used on
   // Linux.
   SkColor thumb_active_color;
   SkColor thumb_inactive_color;
   SkColor track_color;
 
+  // The colors used in selection text. Currently only used on Linux.
+  SkColor active_selection_bg_color;
+  SkColor active_selection_fg_color;
+  SkColor inactive_selection_bg_color;
+  SkColor inactive_selection_fg_color;
+
   // Browser wants a look at all top level requests
   bool browser_handles_top_level_requests;
 
   RendererPreferences()
       : can_accept_load_drops(true),
         should_antialias_text(true),
         hinting(RENDERER_PREFERENCES_HINTING_SYSTEM_DEFAULT),
         subpixel_rendering(
             RENDERER_PREFERENCES_SUBPIXEL_RENDERING_SYSTEM_DEFAULT),
         focus_ring_color(0),
         thumb_active_color(0),
         thumb_inactive_color(0),
         track_color(0),
+        active_selection_bg_color(0),
+        active_selection_fg_color(0),
+        inactive_selection_bg_color(0),
+        inactive_selection_fg_color(0),
         browser_handles_top_level_requests(false) {
   }
 };
 
 #endif  // CHROME_COMMON_RENDERER_PREFERENCES_H_