Replace MessageLoopProxy with ThreadTaskRunnerHandle in src/sync/.

sync/api/attachments/attachment_service_proxy.cc

Index: sync/api/attachments/attachment_service_proxy.cc
diff --git a/sync/api/attachments/attachment_service_proxy.cc b/sync/api/attachments/attachment_service_proxy.cc
index 2477140d1cf5dfb0a06a810b016548dd1a4649ba..4b9bc6786a4b89dd9d37c8940e0df0a049b3254a 100644
--- a/sync/api/attachments/attachment_service_proxy.cc
+++ b/sync/api/attachments/attachment_service_proxy.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
+#include "base/thread_task_runner_handle.h"
 #include "sync/api/sync_data.h"
 
 namespace syncer {
@@ -71,8 +72,10 @@ void AttachmentServiceProxy::GetOrDownloadAttachments(
     const AttachmentIdList& attachment_ids,
     const GetOrDownloadCallback& callback) {
   DCHECK(wrapped_task_runner_);
-  GetOrDownloadCallback proxy_callback = base::Bind(
-      &ProxyGetOrDownloadCallback, base::MessageLoopProxy::current(), callback);
+  GetOrDownloadCallback proxy_callback =
+      base::Bind(&ProxyGetOrDownloadCallback,
+                 base::ThreadTaskRunnerHandle::Get(),
+                 callback);
   wrapped_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&AttachmentService::GetOrDownloadAttachments,
@@ -86,7 +89,7 @@ void AttachmentServiceProxy::DropAttachments(
     const DropCallback& callback) {
   DCHECK(wrapped_task_runner_);
   DropCallback proxy_callback = base::Bind(
-      &ProxyDropCallback, base::MessageLoopProxy::current(), callback);
+      &ProxyDropCallback, base::ThreadTaskRunnerHandle::Get(), callback);
   wrapped_task_runner_->PostTask(FROM_HERE,
                                  base::Bind(&AttachmentService::DropAttachments,
                                             core_,
@@ -98,7 +101,7 @@ void AttachmentServiceProxy::StoreAttachments(const AttachmentList& attachments,
                                               const StoreCallback& callback) {
   DCHECK(wrapped_task_runner_);
   StoreCallback proxy_callback = base::Bind(
-      &ProxyStoreCallback, base::MessageLoopProxy::current(), callback);
+      &ProxyStoreCallback, base::ThreadTaskRunnerHandle::Get(), callback);
   wrapped_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&AttachmentService::StoreAttachments,