Adding instrumentation to locate the source of jankiness.

chrome/browser/extensions/updater/extension_downloader.cc

Index: chrome/browser/extensions/updater/extension_downloader.cc
diff --git a/chrome/browser/extensions/updater/extension_downloader.cc b/chrome/browser/extensions/updater/extension_downloader.cc
index 93cb40d7d66d762a083620e64990db9470e17701..1afcf66726418225934cb6496af4e9ce4c5c2523 100644
--- a/chrome/browser/extensions/updater/extension_downloader.cc
+++ b/chrome/browser/extensions/updater/extension_downloader.cc
@@ -13,6 +13,7 @@
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
+#include "base/profiler/scoped_profile.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -486,6 +487,11 @@ void ExtensionDownloader::CreateManifestFetcher() {
 
 void ExtensionDownloader::OnURLFetchComplete(
     const net::URLFetcher* source) {
+  // TODO(vadimt): Remove ScopedProfile below once crbug.com/422577 is fixed.
+  tracked_objects::ScopedProfile tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "422577 ExtensionDownloader::OnURLFetchComplete"));
+
   VLOG(2) << source->GetResponseCode() << " " << source->GetURL();
 
   if (source == manifest_fetcher_.get()) {