Add UMA histograms for Google cached copy experiment on network error interstitial

chrome/renderer/net/net_error_page_controller.cc

Index: chrome/renderer/net/net_error_page_controller.cc
diff --git a/chrome/renderer/net/net_error_page_controller.cc b/chrome/renderer/net/net_error_page_controller.cc
index b06bfd01adfe62213153d8b977eda5a541cb45b9..2f690c2643538e28413038bcbdcb6ba034198aae 100644
--- a/chrome/renderer/net/net_error_page_controller.cc
+++ b/chrome/renderer/net/net_error_page_controller.cc
@@ -52,6 +52,12 @@ bool NetErrorPageController::TrackEasterEgg() {
   return ButtonClick(error_page::NetErrorHelperCore::EASTER_EGG);
 }
 
+bool NetErrorPageController::TrackCachedCopyButtonClick(bool is_default_label) {
+  return is_default_label ?
+      ButtonClick(error_page::NetErrorHelperCore::SHOW_CACHED_PAGE_BUTTON) :
+      ButtonClick(error_page::NetErrorHelperCore::SHOW_CACHED_COPY_BUTTON);
+}
+
 bool NetErrorPageController::TrackClick(const gin::Arguments& args) {
   if (!render_frame())
     return false;
@@ -98,7 +104,9 @@ gin::ObjectTemplateBuilder NetErrorPageController::GetObjectTemplateBuilder(
       .SetMethod("trackClick",
                  &NetErrorPageController::TrackClick)
       .SetMethod("trackEasterEgg",
-                 &NetErrorPageController::TrackEasterEgg);
+                 &NetErrorPageController::TrackEasterEgg)
+      .SetMethod("trackCachedCopyButtonClick",
+                 &NetErrorPageController::TrackCachedCopyButtonClick);
 }
 
 void NetErrorPageController::OnDestruct() {}