Change some desktop notifications layout parameters to be per-platform rather...

chrome/browser/notifications/balloon_collection_win.cc

Index: chrome/browser/notifications/balloon_collection_win.cc
===================================================================
--- chrome/browser/notifications/balloon_collection_win.cc	(revision 38514)
+++ chrome/browser/notifications/balloon_collection_win.cc	(working copy)
@@ -17,3 +17,15 @@
   balloon->set_content_size(size);
   return balloon;
 }
+
+int BalloonCollectionImpl::Layout::InterBalloonMargin() const {
+  return 5;
+}
+
+int BalloonCollectionImpl::Layout::HorizontalEdgeMargin() const {
+  return 5;
+}
+
+int BalloonCollectionImpl::Layout::VerticalEdgeMargin() const {
+  return 5;
+}