Avoid string copies when determining approximate memory usage in RDHI

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index 6b3e7706856ae695d8ca4f5b78da5bc023248c94..5a0904a124fe6994b485ab96fe1165090edae3f3 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -100,6 +100,7 @@
 #include "net/base/upload_data_stream.h"
 #include "net/cert/cert_status_flags.h"
 #include "net/cookies/cookie_monster.h"
+#include "net/http/http_request_headers.h"
 #include "net/http/http_response_headers.h"
 #include "net/http/http_response_info.h"
 #include "net/ssl/client_cert_store.h"
@@ -113,6 +114,7 @@
 #include "storage/browser/blob/shareable_file_reference.h"
 #include "storage/browser/fileapi/file_permission_policy.h"
 #include "storage/browser/fileapi/file_system_context.h"
+#include "url/third_party/mozilla/url_parse.h"
 #include "url/url_constants.h"
 
 using base::Time;
@@ -2330,10 +2332,15 @@ int ResourceDispatcherHostImpl::CalculateApproximateMemoryCost(
   // The following fields should be a minor size contribution (experimentally
   // on the order of 100). However since they are variable length, it could
   // in theory be a sizeable contribution.
-  int strings_cost = request->extra_request_headers().ToString().size() +
-                     request->original_url().spec().size() +
-                     request->referrer().size() +
-                     request->method().size();
+  int header_length = 0;

[Randy Smith (Not in Mondays), 2016/11/16 13:07:04]

Suggestion: Make this declaration string_cost and use the "string_cost += "
idiom regularly below.  It removes a variable (which I think is good all other
things being equal to reduce conceptual complexity) and makes the accumulation
style consistent.  Very much a matter of personal style, so up to you.

[Charlie Harrison, 2016/11/16 13:55:44]

Done.

+  for (net::HttpRequestHeaders::Iterator it(request->extra_request_headers());
+       it.GetNext();) {
+    header_length += it.name().length() + it.value().length();
+  }
+  int strings_cost =
+      header_length +
+      request->original_url().parsed_for_possibly_invalid_spec().Length() +
+      request->referrer().size() + request->method().size();
 
   // Note that this expression will typically be dominated by:
   // |kAvgBytesPerOutstandingRequest|.