Implement PrintBrowser functionality.

chrome/browser/printing/print_preview_message_handler.h

Index: chrome/browser/printing/print_preview_message_handler.h
diff --git a/chrome/browser/printing/print_preview_message_handler.h b/chrome/browser/printing/print_preview_message_handler.h
index ba7102008ba757b99ccff509e0f5e00690d97321..272113e7a6d56ff883327d43415b6b963f145e51 100644
--- a/chrome/browser/printing/print_preview_message_handler.h
+++ b/chrome/browser/printing/print_preview_message_handler.h
@@ -9,6 +9,7 @@
 #include "base/macros.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
+#include "printing/features/features.h"
 
 class PrintPreviewUI;
 struct PrintHostMsg_DidGetPreviewPageCount_Params;
@@ -38,6 +39,12 @@ class PrintPreviewMessageHandler
   ~PrintPreviewMessageHandler() override;
 
   // content::WebContentsObserver implementation.
+#if BUILDFLAG(ENABLE_PRINT_BROWSER)
+  void DidFinishLoad(content::RenderFrameHost* render_frame_host,
+                     const GURL& validated_url) override;
+#endif
+
+  // content::WebContentsObserver implementation.
   bool OnMessageReceived(const IPC::Message& message,
                          content::RenderFrameHost* render_frame_host) override;