Have media gallery (through native media file util) use MIME sniffer

chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc

Index: chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
diff --git a/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc b/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
index 45345e70ef8cdaac52c0e05c00cea7e9c4ca45fa..dcb7bfcf23ee33e487b265fe593520af0e23a371 100644
--- a/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
+++ b/chrome/browser/media_galleries/fileapi/device_media_async_file_util.cc
@@ -12,12 +12,14 @@
 #include "chrome/browser/media_galleries/fileapi/media_path_filter.h"
 #include "chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h"
 #include "chrome/browser/media_galleries/fileapi/mtp_device_map_service.h"
+#include "chrome/browser/media_galleries/fileapi/native_media_file_util.h"
 #include "webkit/blob/shareable_file_reference.h"
 #include "webkit/fileapi/file_system_context.h"
 #include "webkit/fileapi/file_system_operation_context.h"
 #include "webkit/fileapi/file_system_task_runners.h"
 #include "webkit/fileapi/file_system_url.h"
 #include "webkit/fileapi/isolated_context.h"
+#include "webkit/fileapi/native_file_util.h"
 
 using fileapi::FileSystemOperationContext;
 using fileapi::FileSystemURL;
@@ -316,11 +318,34 @@ void DeviceMediaAsyncFileUtil::OnDidCreateSnapshotFile(
     const base::FilePath& platform_path) {
   if (callback.is_null())
     return;
-  callback.Run(base::PLATFORM_FILE_OK, file_info, platform_path,
-               ShareableFileReference::GetOrCreate(
-                   platform_path,
-                   ShareableFileReference::DELETE_ON_FINAL_RELEASE,
-                   media_task_runner));
+  base::PlatformFileError* error = new base::PlatformFileError;
+  media_task_runner->PostTaskAndReply(
+          FROM_HERE,
+          base::Bind(&NativeMediaFileUtil::IsMediaFile, platform_path,
+                     base::Unretained(error)),
+          base::Bind(&DeviceMediaAsyncFileUtil::OnDidCheckMedia,
+                     weak_ptr_factory_.GetWeakPtr(),
+                     callback, make_scoped_refptr(media_task_runner),
+                     file_info,
+                     ShareableFileReference::GetOrCreate(
+                         platform_path,
+                         ShareableFileReference::DELETE_ON_FINAL_RELEASE,
+                         media_task_runner),
+                     base::Owned(error)));
+}
+
+void DeviceMediaAsyncFileUtil::OnDidCheckMedia(
+    const AsyncFileUtil::CreateSnapshotFileCallback& callback,
+    base::SequencedTaskRunner* media_task_runner,
+    const base::PlatformFileInfo& file_info,
+    scoped_refptr<webkit_blob::ShareableFileReference> platform_file,
+    base::PlatformFileError* error) {
+  if (callback.is_null())
+    return;
+  base::FilePath platform_path(platform_file.get()->path());
+  if (*error != base::PLATFORM_FILE_OK)
+    platform_file = NULL;
+  callback.Run(*error, file_info, platform_path, platform_file);
 }
 
 void DeviceMediaAsyncFileUtil::OnCreateSnapshotFileError(