Add metrics for DHCP WPAD feature.

net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc

 // Copyright (c) 2011 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 "net/proxy/dhcp_proxy_script_adapter_fetcher_win.h"
 
 #include "base/message_loop_proxy.h"
+#include "base/metrics/histogram.h"
 #include "base/sys_string_conversions.h"
 #include "base/task.h"
 #include "base/threading/worker_pool.h"
 #include "base/time.h"
 #include "net/base/net_errors.h"
 #include "net/proxy/dhcpcsvc_init_win.h"
 #include "net/proxy/proxy_script_fetcher_impl.h"
 #include "net/url_request/url_request_context.h"
 
 #include <windows.h>
@@ skipping 244 matching lines @@
                               NULL,
                               const_cast<LPWSTR>(adapter_name_wide.c_str()),
                               NULL,
                               send_params, request_params,
                               result_buffer.get(), &result_buffer_size,
                               NULL);
     ++retry_count;
   } while (res == ERROR_MORE_DATA && retry_count <= 3);
 
   if (res != NO_ERROR) {
-    NOTREACHED();
+    LOG(INFO) << "Error fetching PAC URL from DHCP: " << res;
+    UMA_HISTOGRAM_COUNTS("Net.DhcpWpadUnhandledDhcpError", 1);
   } else if (wpad_params.nBytesData) {
     // The result should be ASCII, not wide character.
     DCHECK_EQ(strlen(reinterpret_cast<const char*>(wpad_params.Data)) + 1,
               wpad_params.nBytesData);
     // Return only up to the first null in case of embedded NULLs; if the
     // server is giving us back a buffer with embedded NULLs, something is
     // broken anyway.
     return std::string(reinterpret_cast<const char *>(wpad_params.Data));
   }
 
   return "";
 }
 
 }  // namespace net