arc: Delete print document on non-UI thread

Ensure the print document is being deleted on a non-UI thread when the
print session ends.

Bug: b:139551164
Test: Close print preview and verify print document is deleted
Change-Id: I4e0afbaf2942b7a2fb89b319a3885855243963d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787558
Commit-Queue: Jesse Schettler <jschettler@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#694236}

chrome/browser/chromeos/arc/print_spooler/arc_print_spooler_util.cc

@@ -15,6 +15,11 @@
 
 namespace arc {
 
+void DeletePrintDocument(const base::FilePath& file_path) {
+  if (!base::DeleteFile(file_path, false))
+    LOG(ERROR) << "Failed to delete print document.";
+}
+
 base::FilePath SavePrintDocument(mojo::ScopedHandle scoped_handle) {
   base::PlatformFile platform_file = base::kInvalidPlatformFile;
   if (mojo::UnwrapPlatformFile(std::move(scoped_handle), &platform_file) !=

chrome/browser/chromeos/arc/print_spooler/arc_print_spooler_util.h

@@ -15,6 +15,9 @@ class FilePath;
 
 namespace arc {
 
+// Deletes a print document and logs any errors.
+void DeletePrintDocument(const base::FilePath& file_path);
+
 // Uses the provided scoped handle to save a print document from ARC and returns
 // the document's file path.
 base::FilePath SavePrintDocument(mojo::ScopedHandle scoped_handle);

chrome/browser/chromeos/arc/print_spooler/print_session_impl.cc

@@ -9,11 +9,13 @@
 #include "ash/public/cpp/arc_custom_tab.h"
 #include "base/bind.h"
 #include "base/files/file_path.h"
-#include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
+#include "base/task/post_task.h"
+#include "base/task/task_traits.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
+#include "chrome/browser/chromeos/arc/print_spooler/arc_print_spooler_util.h"
 #include "chrome/browser/printing/print_view_manager_common.h"
 #include "content/public/browser/web_contents.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
@@ -71,8 +73,8 @@ PrintSessionImpl::~PrintSessionImpl() {
     return;
   }
 
-  if (!base::DeleteFile(file_path, false))
-    LOG(ERROR) << "Failed to delete print document.";
+  base::PostTask(FROM_HERE, {base::ThreadPool(), base::MayBlock()},
+                 base::BindOnce(&DeletePrintDocument, file_path));
 }
 
 void PrintSessionImpl::Close() {