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

chrome/common/renderer_preferences.h

Index: chrome/common/renderer_preferences.h
diff --git a/chrome/common/renderer_preferences.h b/chrome/common/renderer_preferences.h
index a982d57700d3a7c883b0a23c528927acd62dd42a..30b267feabf17ea2fcc18346eda2d15301459309 100644
--- a/chrome/common/renderer_preferences.h
+++ b/chrome/common/renderer_preferences.h
@@ -57,6 +57,12 @@ struct RendererPreferences {
   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;
 
@@ -70,6 +76,10 @@ struct RendererPreferences {
         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) {
   }
 };