Adding instrumentation to locate the source of jankiness.

extensions/browser/extension_protocols.cc

Index: extensions/browser/extension_protocols.cc
diff --git a/extensions/browser/extension_protocols.cc b/extensions/browser/extension_protocols.cc
index 351047ecf844c19ef3e7a9a641ff31478cbc63eb..f91ab116655916f54945685726494a2b67c37de7 100644
--- a/extensions/browser/extension_protocols.cc
+++ b/extensions/browser/extension_protocols.cc
@@ -20,6 +20,7 @@
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/path_service.h"
+#include "base/profiler/scoped_profile.h"
 #include "base/sha1.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
@@ -87,6 +88,11 @@ class GeneratedBackgroundPageJob : public net::URLRequestSimpleJob {
                       std::string* charset,
                       std::string* data,
                       const net::CompletionCallback& callback) const override {
+    // TODO(vadimt): Remove ScopedProfile below once crbug.com/422489 is fixed.
+    tracked_objects::ScopedProfile tracking_profile(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION(
+            "422489 GeneratedBackgroundPageJob::GetData"));
+
     *mime_type = "text/html";
     *charset = "utf-8";