Add more out of line copy ctors for complex classes.

cc/surfaces/surface_manager.h

Index: cc/surfaces/surface_manager.h
diff --git a/cc/surfaces/surface_manager.h b/cc/surfaces/surface_manager.h
index 8ddace4ff158f93c5806624c551347c446fe49c4..55e44f8fb03016e7f4ec6e32a4dede8b6a589c4d 100644
--- a/cc/surfaces/surface_manager.h
+++ b/cc/surfaces/surface_manager.h
@@ -126,6 +126,7 @@ class CC_SURFACES_EXPORT SurfaceManager {
   // pointers guaranteed alive by callers until unregistered.
   struct ClientSourceMapping {
     ClientSourceMapping();
+    ClientSourceMapping(const ClientSourceMapping& other);
     ~ClientSourceMapping();
     bool is_empty() const { return !client && !children.size(); }
     // The client that's responsible for creating this namespace.  Never null.