Add range check to allow for NULL to be counted as data or not by DHCP server.

net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc

Index: net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc
diff --git a/net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc b/net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc
index 32baeb7a634dbd85a67efaaf7de4a74b912dcadc..da19216a95aa89a01a11c4359ef91481b8b6b79a 100644
--- a/net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc
+++ b/net/proxy/dhcp_proxy_script_adapter_fetcher_win.cc
@@ -265,9 +265,15 @@ std::string DhcpProxyScriptAdapterFetcher::GetPacURLFromDhcp(
     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);
+#ifndef NDEBUG
+    // The result should be ASCII, not wide character.  Some DHCP
+    // servers appear to count the trailing NULL in nBytesData, others
+    // do not.
+    size_t count_without_null =
+        strlen(reinterpret_cast<const char*>(wpad_params.Data));
+    DCHECK(count_without_null == wpad_params.nBytesData ||
+           count_without_null + 1 == wpad_params.nBytesData);
+#endif
     // 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.