Implement dragging icon for dragging bookmarks in views/gtk.

app/os_exchange_data_provider_gtk.cc

Index: app/os_exchange_data_provider_gtk.cc
===================================================================
--- app/os_exchange_data_provider_gtk.cc	(revision 28576)
+++ app/os_exchange_data_provider_gtk.cc	(working copy)
@@ -16,15 +16,23 @@
     const std::set<GdkAtom>& known_custom_formats)
     : known_formats_(known_formats),
       known_custom_formats_(known_custom_formats),
-      formats_(0) {
+      formats_(0),
+      drag_image_(NULL),
+      cursor_offset_x_(0),
+      cursor_offset_y_(0) {
 }
 
 OSExchangeDataProviderGtk::OSExchangeDataProviderGtk()
     : known_formats_(0),
-      formats_(0) {
+      formats_(0),
+      drag_image_(NULL),
+      cursor_offset_x_(0),
+      cursor_offset_y_(0) {
 }
 
 OSExchangeDataProviderGtk::~OSExchangeDataProviderGtk() {
+  if (drag_image_)
+    g_object_unref(drag_image_);
 }
 
 bool OSExchangeDataProviderGtk::HasDataForAllFormats(
@@ -218,6 +226,17 @@
   return true;
 }
 
+void OSExchangeDataProviderGtk::SetDragImage(GdkPixbuf* drag_image,
+                                             int cursor_offset_x,
+                                             int cursor_offset_y) {
+  if (drag_image_)
+    g_object_unref(drag_image_);
+  g_object_ref(drag_image);
+  drag_image_ = drag_image;
+  cursor_offset_x_ = cursor_offset_x;
+  cursor_offset_y_ = cursor_offset_y;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // OSExchangeData, public: