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

chrome/browser/ui/webui/favicon_source.cc

Index: chrome/browser/ui/webui/favicon_source.cc
diff --git a/chrome/browser/ui/webui/favicon_source.cc b/chrome/browser/ui/webui/favicon_source.cc
index 649526c5a06024608b01780dfa313e15ffd04f6b..8fb8356e44b3990b21e4f14d48b4524c447199c8 100644
--- a/chrome/browser/ui/webui/favicon_source.cc
+++ b/chrome/browser/ui/webui/favicon_source.cc
@@ -42,6 +42,8 @@ FaviconSource::IconRequest::IconRequest(
       device_scale_factor(scale) {
 }
 
+FaviconSource::IconRequest::IconRequest(const IconRequest& other) = default;
+
 FaviconSource::IconRequest::~IconRequest() {
 }