chrome: Add out-of-line copy ctors for complex classes.

chrome/utility/media_galleries/ipc_data_source.h

Index: chrome/utility/media_galleries/ipc_data_source.h
diff --git a/chrome/utility/media_galleries/ipc_data_source.h b/chrome/utility/media_galleries/ipc_data_source.h
index ff00484c94a3d08a141d318044402bab0801abc1..a6aac618944186421600c6cbae3a6baccf65e949 100644
--- a/chrome/utility/media_galleries/ipc_data_source.h
+++ b/chrome/utility/media_galleries/ipc_data_source.h
@@ -50,6 +50,7 @@ class IPCDataSource: public media::DataSource,
  private:
   struct Request {
     Request();
+    Request(const Request& other);
     ~Request();
     uint8_t* destination;
     ReadCB callback;