Adding instrumentation to locate the source of jankiness.

chrome/browser/extensions/chrome_url_request_util.cc

 // Copyright 2014 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/extensions/chrome_url_request_util.h"
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 51 matching lines @@
   int GetData(std::string* mime_type,
               std::string* charset,
               std::string* data,
               const net::CompletionCallback& callback) const override {
     // TODO(vadimt): Remove ScopedTracker below once crbug.com/422489 is fixed.
     tracked_objects::ScopedTracker tracking_profile(
         FROM_HERE_WITH_EXPLICIT_FUNCTION(
             "422489 URLRequestResourceBundleJob::GetData"));
 
     const ResourceBundle& rb = ResourceBundle::GetSharedInstance();
+
+    // TODO(vadimt): Remove ScopedTracker below once crbug.com/422489 is fixed.
+    tracked_objects::ScopedTracker tracking_profile1(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "422489 URLRequestResourceBundleJob::GetData 1"));
+
     *data = rb.GetRawDataResource(resource_id_).as_string();
 
+    // TODO(vadimt): Remove ScopedTracker below once crbug.com/422489 is fixed.
+    tracked_objects::ScopedTracker tracking_profile2(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "422489 URLRequestResourceBundleJob::GetData 2"));
+
     // Add the Content-Length header now that we know the resource length.
     response_info_.headers->AddHeader(
         base::StringPrintf("%s: %s",
                            net::HttpRequestHeaders::kContentLength,
                            base::UintToString(data->size()).c_str()));
 
+    // TODO(vadimt): Remove ScopedTracker below once crbug.com/422489 is fixed.
+    tracked_objects::ScopedTracker tracking_profile3(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "422489 URLRequestResourceBundleJob::GetData 3"));
+
     std::string* read_mime_type = new std::string;
     bool posted = base::PostTaskAndReplyWithResult(
         BrowserThread::GetBlockingPool(),
         FROM_HERE,
         base::Bind(&net::GetMimeTypeFromFile,
                    filename_,
                    base::Unretained(read_mime_type)),

[not at google - send to devlin, 2014/10/29 23:34:16]

(hopefully it's not one of these Binds, in which case you'd need to assign them
to local variables and instrument each separately, but that's likely overkill)

[vadimt, 2014/10/29 23:38:20]

Acknowledged.

         base::Bind(&URLRequestResourceBundleJob::OnMimeTypeRead,
                    weak_factory_.GetWeakPtr(),
                    mime_type,
                    charset,
                    data,
                    base::Owned(read_mime_type),
                    callback));
     DCHECK(posted);
 
     return net::ERR_IO_PENDING;
@@ skipping 92 matching lines @@
                                              resource_id,
                                              content_security_policy,
                                              send_cors_header);
     }
   }
   return NULL;
 }
 
 }  // namespace chrome_url_request_util
 }  // namespace extensions