arc: Use the MIME type returned by the container to handle content URLs

chrome/browser/chromeos/arc/fileapi/arc_file_system_operation_runner.cc

 // Copyright 2017 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 "chrome/browser/chromeos/arc/fileapi/arc_file_system_operation_runner.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 86 matching lines @@
   auto* file_system_instance = ARC_GET_INSTANCE_FOR_METHOD(
       arc_bridge_service()->file_system(), GetFileSize);
   if (!file_system_instance) {
     base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
                                                   base::BindOnce(callback, -1));
     return;
   }
   file_system_instance->GetFileSize(url.spec(), callback);
 }
 
+void ArcFileSystemOperationRunner::GetMimeType(
+    const GURL& url,
+    const GetMimeTypeCallback& callback) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (should_defer_) {
+    deferred_operations_.emplace_back(
+        base::Bind(&ArcFileSystemOperationRunner::GetMimeType,
+                   weak_ptr_factory_.GetWeakPtr(), url, callback));
+    return;
+  }
+  auto* file_system_instance = ARC_GET_INSTANCE_FOR_METHOD(
+      arc_bridge_service()->file_system(), GetMimeType);
+  if (!file_system_instance) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, base::Optional<std::string>()));

[dcheng, 2017/06/01 11:06:44]

Let's use base::nullopt instead of base::Optional<T>()

[hashimoto, 2017/06/01 11:30:16]

Sounds good.
Done.

+    return;
+  }
+  file_system_instance->GetMimeType(url.spec(), callback);
+}
+
 void ArcFileSystemOperationRunner::OpenFileToRead(
     const GURL& url,
     const OpenFileToReadCallback& callback) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   if (should_defer_) {
     deferred_operations_.emplace_back(
         base::Bind(&ArcFileSystemOperationRunner::OpenFileToRead,
                    weak_ptr_factory_.GetWeakPtr(), url, callback));
     return;
   }
@@ skipping 187 matching lines @@
   deferred_operations.swap(deferred_operations_);
   for (const base::Closure& operation : deferred_operations) {
     operation.Run();
   }
 
   // No deferred operations should be left at this point.
   DCHECK(deferred_operations_.empty());
 }
 
 }  // namespace arc