Remove modules/filesystem/DraggedIsolatedFileSystem.h dependency from core/DEPS.

Source/modules/filesystem/DataTransferItemFileSystem.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 42 matching lines @@
     if (!item.dataObjectItem()->isFilename())
         return nullptr;
 
     // For dragged files getAsFile must be pretty lightweight.
     Blob* file = item.getAsFile().get();
     // The clipboard may not be in a readable state.
     if (!file)
         return nullptr;
     ASSERT(file->isFile());
 
-    DraggedIsolatedFileSystem* filesystem = DraggedIsolatedFileSystem::from(item.clipboard()->dataObject().get());
-    DOMFileSystem* domFileSystem = filesystem ? filesystem->getDOMFileSystem(executionContext) : 0;
-    if (!filesystem) {
+    DOMFileSystem* domFileSystem = DraggedIsolatedFileSystem::getDOMFileSystem(item.clipboard()->dataObject().get(), executionContext);
+    if (!domFileSystem) {
         // IsolatedFileSystem may not be enabled.
         return nullptr;
     }
 
-    ASSERT(domFileSystem);
-
     // The dropped entries are mapped as top-level entries in the isolated filesystem.
     String virtualPath = DOMFilePath::append("/", toFile(file)->name());
 
     // FIXME: This involves synchronous file operation. Consider passing file type data when we dispatch drag event.
     FileMetadata metadata;
     if (!getFileMetadata(toFile(file)->path(), metadata))
         return nullptr;
 
     if (metadata.type == FileMetadata::TypeDirectory)
         return DirectoryEntry::create(domFileSystem, virtualPath);
     return FileEntry::create(domFileSystem, virtualPath);
 }
 
 } // namespace WebCore