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

printing/backend/print_backend.cc

Index: printing/backend/print_backend.cc
diff --git a/printing/backend/print_backend.cc b/printing/backend/print_backend.cc
index fefa7899eb3456f47a71114725ff0666427118ec..6c43b648f8777b8289a44d98b12e0b3ab15f3a0b 100644
--- a/printing/backend/print_backend.cc
+++ b/printing/backend/print_backend.cc
@@ -10,6 +10,8 @@ PrinterBasicInfo::PrinterBasicInfo()
     : printer_status(0),
       is_default(false) {}
 
+PrinterBasicInfo::PrinterBasicInfo(const PrinterBasicInfo& other) = default;
+
 PrinterBasicInfo::~PrinterBasicInfo() {}
 
 PrinterSemanticCapsAndDefaults::PrinterSemanticCapsAndDefaults()
@@ -28,6 +30,9 @@ PrinterSemanticCapsAndDefaults::~PrinterSemanticCapsAndDefaults() {}
 
 PrinterCapsAndDefaults::PrinterCapsAndDefaults() {}
 
+PrinterCapsAndDefaults::PrinterCapsAndDefaults(
+    const PrinterCapsAndDefaults& other) = default;
+
 PrinterCapsAndDefaults::~PrinterCapsAndDefaults() {}
 
 PrintBackend::~PrintBackend() {}