Avoid string copies when determining approximate memory usage in RDHI

content/browser/loader/resource_dispatcher_host_impl.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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 
 #include <stddef.h>
 
@@ skipping 82 matching lines @@
 #include "ipc/ipc_message_start.h"
 #include "net/base/auth.h"
 #include "net/base/load_flags.h"
 #include "net/base/mime_util.h"
 #include "net/base/net_errors.h"
 #include "net/base/registry_controlled_domains/registry_controlled_domain.h"
 #include "net/base/request_priority.h"
 #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"
 #include "net/ssl/ssl_cert_request_info.h"
 #include "net/url_request/url_request.h"
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_job_factory.h"
 #include "storage/browser/blob/blob_data_handle.h"
 #include "storage/browser/blob/blob_storage_context.h"
 #include "storage/browser/blob/blob_url_request_job_factory.h"
 #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;
 using base::TimeDelta;
 using base::TimeTicks;
 using storage::ShareableFileReference;
 using SyncLoadResultCallback =
     content::ResourceDispatcherHostImpl::SyncLoadResultCallback;
 
 // ----------------------------------------------------------------------------
@@ skipping 2197 matching lines @@
                nullptr, nullptr);
   filter_ = nullptr;
 }
 
 // static
 int ResourceDispatcherHostImpl::CalculateApproximateMemoryCost(
     net::URLRequest* request) {
   // 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|.
   return kAvgBytesPerOutstandingRequest + strings_cost;
 }
 
 void ResourceDispatcherHostImpl::BeginRequestInternal(
     std::unique_ptr<net::URLRequest> request,
     std::unique_ptr<ResourceHandler> handler) {
   DCHECK(!request->is_pending());
@@ skipping 444 matching lines @@
                                  &throttles);
     if (!throttles.empty()) {
       handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                                   std::move(throttles)));
     }
   }
   return handler;
 }
 
 }  // namespace content