Adding instrumentation to locate the source of jankiness.

content/child/web_data_consumer_handle_impl.cc

Index: content/child/web_data_consumer_handle_impl.cc
diff --git a/content/child/web_data_consumer_handle_impl.cc b/content/child/web_data_consumer_handle_impl.cc
index a26656ed3101a4bb855d7225651a2be38befd68b..a310238d67c00ca0b7bfca8427108b47d8673566 100644
--- a/content/child/web_data_consumer_handle_impl.cc
+++ b/content/child/web_data_consumer_handle_impl.cc
@@ -7,6 +7,7 @@
 #include <limits>
 #include "base/bind.h"
 #include "base/logging.h"
+#include "base/profiler/scoped_tracker.h"
 #include "third_party/mojo/src/mojo/public/c/system/types.h"
 
 namespace content {
@@ -109,6 +110,11 @@ Result WebDataConsumerHandleImpl::HandleReadResult(MojoResult mojo_result) {
 }
 
 void WebDataConsumerHandleImpl::OnHandleGotReadable(MojoResult) {
+  // TODO(pkasting): Remove ScopedTracker below once crbug.com/455434 is
+  // fixed.
+  tracked_objects::ScopedTracker tracking_profile(
+      FROM_HERE_WITH_EXPLICIT_FUNCTION(
+          "455434 WebDataConsumerHandleImpl::OnHandleGotReadable"));
   DCHECK(client_);
   client_->didGetReadable();
 }