Add histogram for safebrowsing download ping payload size.

chrome/browser/safe_browsing/download_protection_service.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/safe_browsing/download_protection_service.h"
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/format_macros.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 650 matching lines @@
             << item_->GetUrlChain().back();
     fetcher_.reset(net::URLFetcher::Create(0 /* ID used for testing */,
                                            GURL(GetDownloadRequestUrl()),
                                            net::URLFetcher::POST,
                                            this));
     fetcher_->SetLoadFlags(net::LOAD_DISABLE_CACHE);
     fetcher_->SetAutomaticallyRetryOn5xx(false);  // Don't retry on error.
     fetcher_->SetRequestContext(service_->request_context_getter_.get());
     fetcher_->SetUploadData("application/octet-stream",
                             client_download_request_data_);
+    UMA_HISTOGRAM_COUNTS("SBClientDownload.DownloadRequestPayloadSize",
+                         client_download_request_data_.size());

[Ilya Sherman, 2013/07/30 01:27:39]

Are you sure that a histogram mapping [1, 1,000,000) bytes gives you the dynamic
range that you want?  It seems likely to me that you might not care so much
about distinguishing payload sizes on the order of 1-10 bytes, and possibly care
about distinguishing payload sizes on the order of 1-10 megabytes.  If so, you
might want to switch this histogram to measure KB instead of just bytes.

[mattm, 2013/07/30 01:53:23]

This is actually the size of the ping we send to the safebrowsing server, not
the size of the file we are checking, so it shouldn't be that big.

     fetcher_->Start();
   }
 
   void PostFinishTask(DownloadCheckResult result,
                       DownloadCheckResultReason reason) {
     BrowserThread::PostTask(
         BrowserThread::UI,
         FROM_HERE,
         base::Bind(&CheckClientDownloadRequest::FinishRequest, this, result,
                    reason));
@@ skipping 288 matching lines @@
   std::string url = kDownloadRequestUrl;
   std::string api_key = google_apis::GetAPIKey();
   if (!api_key.empty()) {
     base::StringAppendF(&url, "?key=%s",
                         net::EscapeQueryParamValue(api_key, true).c_str());
   }
   return url;
 }
 
 }  // namespace safe_browsing