HTML MessagePort as mojo::MessagePipeHandle

content/child/blob_storage/blob_transport_controller.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/child/blob_storage/blob_transport_controller.h"
 
 #include <limits>
 #include <memory>
 #include <utility>
 #include <vector>
@@ skipping 163 matching lines @@
   BlobTransportController::GetDescriptions(
       consolidation.get(), quotas.max_ipc_memory_size, &descriptions);
   // I post the task first to make sure that we store our consolidation before
   // we get a request back from the browser.
   io_runner->PostTask(
       FROM_HERE,
       base::Bind(&BlobTransportController::StoreBlobDataForRequests,
                  base::Unretained(BlobTransportController::GetInstance()), uuid,
                  base::Passed(std::move(consolidation)),
                  base::Passed(std::move(main_runner))));
+
+  // Measure how much jank this synchronous IPC is introducing.
+  base::TimeTicks time_before = base::TimeTicks::Now();

[Alexei Svitkine (slow), 2017/02/08 19:29:29]

Nit: You can make this a bit simpler by using
SCOPED_UMA_HISTOGRAM_TIMER("Storage.Blob.RegisterBlobTime");

+
   sender->Send(
       new BlobStorageMsg_RegisterBlob(uuid, content_type, "", descriptions));
+
+  base::TimeDelta time_delta = base::TimeTicks::Now() - time_before;
+  UMA_HISTOGRAM_TIMES("Storage.Blob.RegisterBlobTime", time_delta);
 }
 
 void BlobTransportController::OnMemoryRequest(
     const std::string& uuid,
     const std::vector<storage::BlobItemBytesRequest>& requests,
     std::vector<base::SharedMemoryHandle>* memory_handles,
     const std::vector<IPC::PlatformFileForTransit>& file_handles,
     base::TaskRunner* file_runner,
     IPC::Sender* sender) {
   std::vector<BlobItemBytesResponse> responses;
@@ skipping 210 matching lines @@
 
 void BlobTransportController::ReleaseBlobConsolidation(
     const std::string& uuid) {
   if (blob_storage_.erase(uuid)) {
     main_thread_runner_->PostTask(FROM_HERE,
                                   base::Bind(&DecChildProcessRefCount));
   }
 }
 
 }  // namespace content