Redesigned and refactored ScopedMTPDeviceMapEntry, MTPDeviceMapService & MTPDeviceDelegate classes.

webkit/fileapi/media/device_media_file_util.cc

Index: webkit/fileapi/media/device_media_file_util.cc
diff --git a/webkit/fileapi/media/device_media_file_util.cc b/webkit/fileapi/media/device_media_file_util.cc
index 6283bff5f4d449460a92c0507fa098bf3ade8ba8..42908081f08160cfd457bbc3ec07210bb1a460f0 100644
--- a/webkit/fileapi/media/device_media_file_util.cc
+++ b/webkit/fileapi/media/device_media_file_util.cc
@@ -63,7 +63,9 @@ PlatformFileError DeviceMediaFileUtil::GetFileInfo(
     const FileSystemURL& url,
     PlatformFileInfo* file_info,
     FilePath* platform_path) {
-  DCHECK(context->mtp_device_delegate());
+  if (!context->mtp_device_delegate().get())
+    return base::PLATFORM_FILE_ERROR_NOT_FOUND;

[Lei Zhang, 2012/11/21 01:33:30]

Perhaps PLATFORM_FILE_ERROR_FAILED is more appropriate? Ditto below.

[kmadhusu, 2012/11/21 04:09:53]

kinuko preferred base::PLATFORM_FILE_ERROR_NOT_FOUND in CreateSnapshotFile. So,
I used the same in GetFileInfo().

If the extension requesting the file information has valid file system access
permissions, then the only reason |mtp_device_delgate().get()| can be NULL is
when the attached MTP device is no longer available to complete the given
request. Therefore, base::PLATFORM_FILE_ERROR_NOT_FOUND seems more relevant to
the context rather than a generic base::PLATFORM_FILE_ERROR_FAILED message.

+
   PlatformFileError error =
       context->mtp_device_delegate()->GetFileInfo(url.path(), file_info);
   if (error != base::PLATFORM_FILE_OK)
@@ -80,7 +82,9 @@ scoped_ptr<FileSystemFileUtil::AbstractFileEnumerator>
         FileSystemOperationContext* context,
         const FileSystemURL& url,
         bool recursive) {
-  DCHECK(context->mtp_device_delegate());
+  if (!context->mtp_device_delegate().get())
+    return make_scoped_ptr(new FileSystemFileUtil::EmptyFileEnumerator())
+        .PassAs<FileSystemFileUtil::AbstractFileEnumerator>();

[kinuko, 2012/11/20 06:25:33]

nit: hmm... if we're just creating a new scoped_ptr (but not passing rvalues)
just using scoped_ptr<foo>(new bar) would look simpler.

scoped_ptr<FileSystemFileUtil::AbstractFileEnumerator>(new ...)

[kmadhusu, 2012/11/21 04:09:53]

Done.

   return make_scoped_ptr(new FilteringFileEnumerator(
       context->mtp_device_delegate()->CreateFileEnumerator(url.path(),
                                                            recursive),
@@ -113,7 +117,9 @@ PlatformFileError DeviceMediaFileUtil::Truncate(
 bool DeviceMediaFileUtil::IsDirectoryEmpty(
     FileSystemOperationContext* context,
     const FileSystemURL& url) {
-  DCHECK(context->mtp_device_delegate());
+  if (!context->mtp_device_delegate().get())
+    return false;
+
   scoped_ptr<AbstractFileEnumerator> enumerator(
       CreateFileEnumerator(context, url, false));
   FilePath path;
@@ -161,7 +167,8 @@ base::PlatformFileError DeviceMediaFileUtil::CreateSnapshotFile(
   DCHECK(file_info);
   DCHECK(local_path);
   DCHECK(snapshot_policy);
-  DCHECK(context->mtp_device_delegate());
+  if (!context->mtp_device_delegate().get())
+    return base::PLATFORM_FILE_ERROR_NOT_FOUND;
 
   // We return a temporary file as a snapshot.
   *snapshot_policy = FileSystemFileUtil::kSnapshotFileTemporary;