Add the "virtual" keyword on method overrides that are missing it.

chrome/browser/renderer_host/download_resource_handler.h

Index: chrome/browser/renderer_host/download_resource_handler.h
diff --git a/chrome/browser/renderer_host/download_resource_handler.h b/chrome/browser/renderer_host/download_resource_handler.h
index 95c09da280329fe5f366295ed3af4eb891aa8593..3fb69613c420898ebe6650a0a528cecebef01c14 100644
--- a/chrome/browser/renderer_host/download_resource_handler.h
+++ b/chrome/browser/renderer_host/download_resource_handler.h
@@ -34,29 +34,29 @@ class DownloadResourceHandler : public ResourceHandler {
                           bool save_as,
                           const DownloadSaveInfo& save_info);
 
-  bool OnUploadProgress(int request_id, uint64 position, uint64 size);
+  virtual bool OnUploadProgress(int request_id, uint64 position, uint64 size);
 
   // Not needed, as this event handler ought to be the final resource.
-  bool OnRequestRedirected(int request_id, const GURL& url,
-                           ResourceResponse* response, bool* defer);
+  virtual bool OnRequestRedirected(int request_id, const GURL& url,
+                                   ResourceResponse* response, bool* defer);
 
   // Send the download creation information to the download thread.
-  bool OnResponseStarted(int request_id, ResourceResponse* response);
+  virtual bool OnResponseStarted(int request_id, ResourceResponse* response);
 
   // Pass-through implementation.
-  bool OnWillStart(int request_id, const GURL& url, bool* defer);
+  virtual bool OnWillStart(int request_id, const GURL& url, bool* defer);
 
   // Create a new buffer, which will be handed to the download thread for file
   // writing and deletion.
-  bool OnWillRead(int request_id, net::IOBuffer** buf, int* buf_size,
-                  int min_size);
+  virtual bool OnWillRead(int request_id, net::IOBuffer** buf, int* buf_size,
+                          int min_size);
 
-  bool OnReadCompleted(int request_id, int* bytes_read);
+  virtual bool OnReadCompleted(int request_id, int* bytes_read);
 
-  bool OnResponseCompleted(int request_id,
-                           const URLRequestStatus& status,
-                           const std::string& security_info);
-  void OnRequestClosed();
+  virtual bool OnResponseCompleted(int request_id,
+                                   const URLRequestStatus& status,
+                                   const std::string& security_info);
+  virtual void OnRequestClosed();
 
   // If the content-length header is not present (or contains something other
   // than numbers), the incoming content_length is -1 (unknown size).