Adding instrumentation to locate the source of jankiness.

net/proxy/proxy_script_fetcher_impl.cc

Index: net/proxy/proxy_script_fetcher_impl.cc
diff --git a/net/proxy/proxy_script_fetcher_impl.cc b/net/proxy/proxy_script_fetcher_impl.cc
index 0ce507b1488be132dde558cdcb2f9fec019e415d..4e57121f281a0c0629c6d927bd120b2e14209198 100644
--- a/net/proxy/proxy_script_fetcher_impl.cc
+++ b/net/proxy/proxy_script_fetcher_impl.cc
@@ -7,6 +7,7 @@
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/strings/string_util.h"
 #include "net/base/data_url.h"
 #include "net/base/io_buffer.h"
@@ -202,6 +203,11 @@ void ProxyScriptFetcherImpl::OnSSLCertificateError(URLRequest* request,
 }
 
 void ProxyScriptFetcherImpl::OnResponseStarted(URLRequest* request) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 ProxyScriptFetcherImpl::OnResponseStarted"));
+
   DCHECK_EQ(request, cur_request_.get());
 
   if (!request->status().is_success()) {
@@ -237,6 +243,11 @@ void ProxyScriptFetcherImpl::OnResponseStarted(URLRequest* request) {
 
 void ProxyScriptFetcherImpl::OnReadCompleted(URLRequest* request,
                                              int num_bytes) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/423948 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "423948 ProxyScriptFetcherImpl::OnReadCompleted"));
+
   DCHECK_EQ(request, cur_request_.get());
   if (ConsumeBytesRead(request, num_bytes)) {
     // Keep reading.