[BlobStorage] Fix IPC race in sending IPC and posting to IO thread

content/child/blob_storage/blob_transport_controller.cc

Index: content/child/blob_storage/blob_transport_controller.cc
diff --git a/content/child/blob_storage/blob_transport_controller.cc b/content/child/blob_storage/blob_transport_controller.cc
index 0bcadbc85d30e80ac8d13d4cbaad0b5864627a04..c9d89060c08234e6c8360fa559e939d504bfa186 100644
--- a/content/child/blob_storage/blob_transport_controller.cc
+++ b/content/child/blob_storage/blob_transport_controller.cc
@@ -72,22 +72,12 @@ void BlobTransportController::InitiateBlobTransfer(
     main_runner->PostTask(FROM_HERE, base::Bind(&IncChildProcessRefCount));
   }
 
-  std::vector<storage::DataElement> descriptions;
-  std::set<std::string> referenced_blobs = consolidation->referenced_blobs();
-  BlobTransportController::GetDescriptions(
-      consolidation.get(), kBlobStorageIPCThresholdBytes, &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::Bind(&BlobTransportController::InitiateBlobTransferOnIOThread, uuid,
+                 content_type, base::Passed(std::move(consolidation)),
+                 base::Passed(std::move(sender)),
                  base::Passed(std::move(main_runner))));
-  // TODO(dmurph): Merge register and start messages.
-  sender->Send(new BlobStorageMsg_RegisterBlobUUID(uuid, content_type, "",
-                                                   referenced_blobs));
-  sender->Send(new BlobStorageMsg_StartBuildingBlob(uuid, descriptions));
 }
 
 void BlobTransportController::OnMemoryRequest(
@@ -198,6 +188,26 @@ void BlobTransportController::ClearForTesting() {
   blob_storage_.clear();
 }
 
+// static
+void BlobTransportController::InitiateBlobTransferOnIOThread(
+    const std::string& uuid,
+    const std::string& content_type,
+    std::unique_ptr<BlobConsolidation> consolidation,
+    scoped_refptr<ThreadSafeSender> sender,
+    scoped_refptr<base::SingleThreadTaskRunner> main_runner) {
+  std::vector<storage::DataElement> descriptions;
+  std::set<std::string> referenced_blobs = consolidation->referenced_blobs();
+  BlobTransportController::GetDescriptions(
+      consolidation.get(), kBlobStorageIPCThresholdBytes, &descriptions);
+  BlobTransportController::GetInstance()->StoreBlobDataForRequests(
+      uuid, std::move(consolidation), std::move(main_runner));
+
+  // TODO(dmurph): Merge register and start messages.
+  sender->Send(new BlobStorageMsg_RegisterBlobUUID(uuid, content_type, "",
+                                                   referenced_blobs));
+  sender->Send(new BlobStorageMsg_StartBuildingBlob(uuid, descriptions));
+}
+
 void BlobTransportController::StoreBlobDataForRequests(
     const std::string& uuid,
     std::unique_ptr<BlobConsolidation> consolidation,