Detect file system errors during downloads.

content/browser/download/base_file.cc

Index: content/browser/download/base_file.cc
diff --git a/content/browser/download/base_file.cc b/content/browser/download/base_file.cc
index 0a40369c675d4b24f5fac0d14adff45d70ce349c..87d60f85276b4727d2cc658a085e2399e46f40a0 100644
--- a/content/browser/download/base_file.cc
+++ b/content/browser/download/base_file.cc
@@ -203,6 +203,10 @@ void BaseFile::AnnotateWithSourceInformation() {
 #endif
 }
 
+void BaseFile::CreateFileStream() {
+  file_stream_.reset(new net::FileStream);
+}
+
 bool BaseFile::Open() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   DCHECK(!detached_);
@@ -210,7 +214,7 @@ bool BaseFile::Open() {
 
   // Create a new file stream if it is not provided.
   if (!file_stream_.get()) {
-    file_stream_.reset(new net::FileStream);
+    CreateFileStream();
     if (file_stream_->Open(full_path_,
                            base::PLATFORM_FILE_OPEN_ALWAYS |
                                base::PLATFORM_FILE_WRITE) != net::OK) {