GTK: Move CairoCachedSurface from being owned by GtkThemeService to gfx::Image.

ui/gfx/image/image.h

Index: ui/gfx/image/image.h
diff --git a/ui/gfx/image/image.h b/ui/gfx/image/image.h
index c9aff412d292d2e4bc8ac3bf2a85792ac9cfd42f..dd4b8ec771ecd3f9c3d0795d6ad618c2557d2af6 100644
--- a/ui/gfx/image/image.h
+++ b/ui/gfx/image/image.h
@@ -35,6 +35,10 @@ class ImageMacTest;
 
 namespace gfx {
 
+#if defined(TOOLKIT_USES_GTK)
+class CairoCachedSurface;
+#endif
+
 namespace internal {
 class ImageRep;
 class ImageStorage;
@@ -45,6 +49,7 @@ class UI_EXPORT Image {
   enum RepresentationType {
     kImageRepGdk,
     kImageRepCocoa,
+    kImageRepCairoCache,
     kImageRepSkia,
   };
 
@@ -84,6 +89,7 @@ class UI_EXPORT Image {
   const SkBitmap* ToSkBitmap() const;
 #if defined(TOOLKIT_USES_GTK)
   GdkPixbuf* ToGdkPixbuf() const;
+  CairoCachedSurface* const ToCairo() const;
 #elif defined(OS_MACOSX)
   NSImage* ToNSImage() const;
 #endif