Create blobs from Disk Cache entries.

storage/browser/blob/blob_url_request_job.cc

Index: storage/browser/blob/blob_url_request_job.cc
diff --git a/storage/browser/blob/blob_url_request_job.cc b/storage/browser/blob/blob_url_request_job.cc
index d94fa0ba46a67f10bc1e49f6ee1caa06f6b9e530..5796b0419faa272a0718e0c79897315621d43b27 100644
--- a/storage/browser/blob/blob_url_request_job.cc
+++ b/storage/browser/blob/blob_url_request_job.cc
@@ -351,6 +351,8 @@ bool BlobURLRequestJob::ReadItem() {
     return ReadFileItem(GetFileStreamReader(current_item_index_),
                         bytes_to_read);
   }
+  if (item.type() == DataElement::TYPE_DISK_CACHE_ENTRY)
+    return ReadDiskCacheEntryItem(item, bytes_to_read);
   NOTREACHED();
   return false;
 }
@@ -453,6 +455,42 @@ void BlobURLRequestJob::DeleteCurrentFileReader() {
   }
 }
 
+bool BlobURLRequestJob::ReadDiskCacheEntryItem(const BlobDataItem& item,
+                                               int bytes_to_read) {
+  DCHECK_GE(read_buf_->BytesRemaining(), bytes_to_read);
+
+  const int result = item.disk_cache_entry()->ReadData(
+      item.disk_cache_stream_index(), current_item_offset_, read_buf_.get(),
+      bytes_to_read, base::Bind(&BlobURLRequestJob::DidReadDiskCacheEntry,
+                                base::Unretained(this)));

[michaeln, 2015/06/12 22:35:09]

2 questions:

1) How is base::Unretained here safe? I don't think it is.

It's safe in ReadFileItem() because when this class is destructed the
FileStreamReader is deleted so that completion callback won't be called.

In this case, |item| is refcounted and outlives this job. And Entry's are
supposed to invoke the completion callback even after being closed.

WeakPtr?

2) Is it ok to have two ReadData calls pending against the same Entry instance.
Two different jobs could be running at the same time. Pretty sure its ok, but
just checking.

[gavinp, 2015/06/15 14:01:19]

I think you're right. jkarlin first raised this in his review, but I dismissed
it too easily, not seeing the real reason it was safe. WeakPtr.

Done.
Yes, this is OK.

+  DCHECK_LT(result, 0);
+  if (result == net::ERR_IO_PENDING)
+    SetStatus(net::URLRequestStatus(net::URLRequestStatus::IO_PENDING, 0));
+  else
+    NotifyFailure(result);
+  return false;
+}
+
+void BlobURLRequestJob::DidReadDiskCacheEntry(int result) {
+  if (result <= 0) {
+    NotifyFailure(net::ERR_FAILED);
+    return;
+  }
+  SetStatus(net::URLRequestStatus());
+
+  AdvanceBytesRead(result);
+
+  if (!read_buf_->BytesRemaining()) {
+    int bytes_read = BytesReadCompleted();
+    NotifyReadComplete(bytes_read);
+    return;
+  }
+
+  int bytes_read = 0;
+  if (ReadLoop(&bytes_read))
+    NotifyReadComplete(bytes_read);
+}
+
 int BlobURLRequestJob::BytesReadCompleted() {
   int bytes_read = read_buf_->BytesConsumed();
   read_buf_ = NULL;