Downloads: replace BrowserThread::FILE with task scheduler.

content/browser/download/mock_download_file.cc

Index: content/browser/download/mock_download_file.cc
diff --git a/content/browser/download/mock_download_file.cc b/content/browser/download/mock_download_file.cc
index 58edddd8651de905c22516798471e69a9a5d03a8..3251e4e29097ada113842bdd707be46f5560d355 100644
--- a/content/browser/download/mock_download_file.cc
+++ b/content/browser/download/mock_download_file.cc
@@ -3,6 +3,9 @@
 // found in the LICENSE file.
 
 #include "content/browser/download/mock_download_file.h"
+
+#include "base/bind.h"
+#include "content/public/browser/browser_thread.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
 using ::testing::_;
@@ -11,12 +14,17 @@ using ::testing::Return;
 namespace content {
 namespace {
 
-void SuccessRun(
+void SuccessRun(const DownloadFile::InitializeCallback& initialize_callback) {
+  initialize_callback.Run(DOWNLOAD_INTERRUPT_REASON_NONE);
+}
+
+void PostSuccessRun(
     const DownloadFile::InitializeCallback& initialize_callback,
     const DownloadFile::CancelRequestCallback& cancel_request_callback,
     const DownloadItem::ReceivedSlices& received_slices,
     bool is_parallelizable) {
-  initialize_callback.Run(DOWNLOAD_INTERRUPT_REASON_NONE);
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                          base::Bind(&SuccessRun, initialize_callback));
 }
 
 }  // namespace
@@ -25,7 +33,7 @@ MockDownloadFile::MockDownloadFile() {
   // This is here because |Initialize()| is normally called right after
   // construction.
   ON_CALL(*this, Initialize(_, _, _, _))
-      .WillByDefault(::testing::Invoke(SuccessRun));
+      .WillByDefault(::testing::Invoke(PostSuccessRun));
 }
 
 MockDownloadFile::~MockDownloadFile() {