Adding instrumentation to locate the source of jankiness.

content/browser/fileapi/mock_url_request_delegate.cc

Index: content/browser/fileapi/mock_url_request_delegate.cc
diff --git a/content/browser/fileapi/mock_url_request_delegate.cc b/content/browser/fileapi/mock_url_request_delegate.cc
index 97e09f0df6f6285601f55bf3f98337f6399302d4..45d4ae3fe3a3b6161640fdbb5e16490c41fd9445 100644
--- a/content/browser/fileapi/mock_url_request_delegate.cc
+++ b/content/browser/fileapi/mock_url_request_delegate.cc
@@ -4,6 +4,7 @@
 
 #include "mock_url_request_delegate.h"
 
+#include "base/profiler/scoped_tracker.h"
 #include "base/run_loop.h"
 #include "net/base/io_buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -22,6 +23,11 @@ MockURLRequestDelegate::~MockURLRequestDelegate() {
 }
 
 void MockURLRequestDelegate::OnResponseStarted(net::URLRequest* request) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "422516 MockURLRequestDelegate::OnResponseStarted"));
+
   if (request->status().is_success()) {
     EXPECT_TRUE(request->response_headers());
     ReadSome(request);
@@ -32,6 +38,11 @@ void MockURLRequestDelegate::OnResponseStarted(net::URLRequest* request) {
 
 void MockURLRequestDelegate::OnReadCompleted(net::URLRequest* request,
                                              int bytes_read) {
+  // TODO(vadimt): Remove ScopedTracker below once crbug.com/422516 is fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "422516 MockURLRequestDelegate::OnReadCompleted"));
+
   if (bytes_read > 0)
     ReceiveData(request, bytes_read);
   else