Create blobs from Disk Cache entries.

content/browser/loader/upload_data_stream_builder.cc

Index: content/browser/loader/upload_data_stream_builder.cc
diff --git a/content/browser/loader/upload_data_stream_builder.cc b/content/browser/loader/upload_data_stream_builder.cc
index c497c16c0a769ea50c20469ba1fc44e47708dc31..a117075b8ca552433aa5c9c5a5a29cfc653d4308 100644
--- a/content/browser/loader/upload_data_stream_builder.cc
+++ b/content/browser/loader/upload_data_stream_builder.cc
@@ -133,8 +133,9 @@ scoped_ptr<net::UploadDataStream> UploadDataStreamBuilder::Build(
       case ResourceRequestBody::Element::TYPE_BLOB:
         // Blob elements should be resolved beforehand.
         // TODO(dmurph): Create blob reader and store the snapshot in there.
-        NOTREACHED();
-        break;
+      case ResourceRequestBody::Element::TYPE_DISK_CACHE_ENTRY:
+        // Disk cache entries should not be uploaded, instead only requested

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

Once something in blink has a Blob backed by a disk cache entry, what's to
prevent it from uploading it?

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

Unless I'm missing something, there's no code path for it. The only place these
blobs are created is in response to requests for cache storage. How can those
get to the upload handler?

I've updated the comment to just say not implemented.

[gavinp, 2015/06/15 14:25:55]

jkarlin and I just talked this over. It's true that in many cases, blobs coming
from CacheStorage are unblobified and moved as bytes when they go back to the
browser process (see the CacheStorageCache::PutImpl for an example in blink).
However, let's not make all this asymmetry worse; these should be uploadable.

[michaeln, 2015/06/15 22:17:23]

The browser process is a Blob server of sorts and renderers are clients. Once a
blob is created, the browser stores all the data for it. The uuid is passed
to/from renderers as a reference to that data. A blob in a renderer can be
passed by value in many ways: postMessage(blob),
postMessage(objContainingBlobs), xhr.send(blob)
xhr.send(formDataReferringToBlobs). CacheStorageCache::Put takes as input a
reference to a blob that was created elsewhere and copies its bytes into a
diskCache entry. CacheStorageCache::Match later cons's up a new blob around the
diskCache entry and returns the value to the renderer by reference.

With the Cache and CacheStorage API, is it possible for javascript to get a Blob
that is returned by Match()? I've been assuming that it is. If so, then the
upload code is reacachable (afaict).

[michaeln, 2015/06/15 22:18:59]

errr, i meant to say "passed by reference in many ways"

+        // from blink.
       case ResourceRequestBody::Element::TYPE_UNKNOWN:
         NOTREACHED();
         break;