Implement Blob.close().

Source/core/fileapi/File.cpp

Index: Source/core/fileapi/File.cpp
diff --git a/Source/core/fileapi/File.cpp b/Source/core/fileapi/File.cpp
index de776d5acfee62729976119c903e6f667c9a3112..c23d682314f7331f46e4e8826ccc87dfcf4a2be3 100644
--- a/Source/core/fileapi/File.cpp
+++ b/Source/core/fileapi/File.cpp
@@ -225,6 +225,21 @@ void File::captureSnapshot(long long& snapshotSize, double& snapshotModification
     snapshotModificationTime = metadata.modificationTime;
 }
 
+void File::close(ExecutionContext* executionContext)
+{
+    if (!hasBeenClosed()) {
+        // Reset the File to its closed representation, an empty
+        // Blob. The name isn't cleared, as it should still be
+        // available.
+        m_hasBackingFile = false;
+        m_path = String();
+        m_fileSystemURL = KURL();
+        invalidateSnapshotMetadata();
+        m_relativePath = String();
+        Blob::close(executionContext);
+    }
+}
+
 void File::appendTo(BlobData& blobData) const
 {
     if (!m_hasBackingFile) {