Basic DragImage implementation....

chrome/browser/tab_contents/tab_contents_view_mac.mm

Index: chrome/browser/tab_contents/tab_contents_view_mac.mm
===================================================================
--- chrome/browser/tab_contents/tab_contents_view_mac.mm	(revision 41111)
+++ chrome/browser/tab_contents/tab_contents_view_mac.mm	(working copy)
@@ -126,8 +126,11 @@
   *out = [cocoa_view_.get() NSRectToRect:[cocoa_view_.get() bounds]];
 }
 
-void TabContentsViewMac::StartDragging(const WebDropData& drop_data,
-    WebDragOperationsMask allowed_operations) {
+void TabContentsViewMac::StartDragging(
+    const WebDropData& drop_data,
+    WebDragOperationsMask allowed_operations,
+    const SkBitmap& image,
+    const gfx::Point& image_offset) {
   // By allowing nested tasks, the code below also allows Close(),
   // which would deallocate |this|.  The same problem can occur while
   // processing -sendEvent:, so Close() is deferred in that case.
@@ -138,6 +141,7 @@
   // The drag invokes a nested event loop, arrange to continue
   // processing events.
   MessageLoop::ScopedNestableTaskAllower allow(MessageLoop::current());
+  // TODO(estade): make use of |image| and |image_offset|.
   NSDragOperation mask = static_cast<NSDragOperation>(allowed_operations);
   [cocoa_view_ startDragWithDropData:drop_data
                    dragOperationMask:mask];