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

components/nacl/browser/pnacl_host.cc

Index: components/nacl/browser/pnacl_host.cc
diff --git a/components/nacl/browser/pnacl_host.cc b/components/nacl/browser/pnacl_host.cc
index f5f18f30a06bb3d2240a686cfd1c737ee3f6bbe5..ceaaa893e64ce7b5dc655f9b01eb8cddf7b0ba21 100644
--- a/components/nacl/browser/pnacl_host.cc
+++ b/components/nacl/browser/pnacl_host.cc
@@ -99,6 +99,9 @@ PnaclHost::PendingTranslation::PendingTranslation()
       cache_info(nacl::PnaclCacheInfo()) {
 }
 
+PnaclHost::PendingTranslation::PendingTranslation(
+    const PendingTranslation& other) = default;
+
 PnaclHost::PendingTranslation::~PendingTranslation() {
   if (nexe_fd)
     delete nexe_fd;