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

This patch adds out of line copy constructors for classes that our
clang-plugin considers heavy. This is an effort to enable copy
constructor checks by default.

BUG=436357
[email protected], [email protected], [email protected]

Review URL: https://codereview.chromium.org/1731003003

Cr-Commit-Position: refs/heads/master@{#378262}
diff --git a/mojo/edk/system/handle_table.cc b/mojo/edk/system/handle_table.cc
index 7aeca64..e41817d 100644
--- a/mojo/edk/system/handle_table.cc
+++ b/mojo/edk/system/handle_table.cc
@@ -126,6 +126,8 @@
 HandleTable::Entry::Entry(scoped_refptr<Dispatcher> dispatcher)
     : dispatcher(dispatcher) {}
 
+HandleTable::Entry::Entry(const Entry& other) = default;
+
 HandleTable::Entry::~Entry() {}
 
 }  // namespace edk