Blobs: Catching browser-process created Blobs in extension code.

chrome/browser/extensions/blob_holder.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_EXTENSIONS_BLOB_HOLDER_H_
+#define CHROME_BROWSER_EXTENSIONS_BLOB_HOLDER_H_
+
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+namespace content {
+class BlobHandle;
+}
+
+namespace extensions {
+
+// Used for holding onto Blobs created into the browser process until a
+// renderer takes over ownership.
+class BlobHolder : public content::WebContentsObserver,
+                   public content::WebContentsUserData<BlobHolder> {

[michaeln, 2014/05/23 00:12:34]

Since WebContents can outlive/span processes, i think the BlobHandleVector
should be scoped to the RenderProcessHost. RPH derives from SupportsUserData so
this collection of blobhandles in transite to that process could hang there as
UserData.

For processing the AckMessage in the browser process, ExtensionMessageFilter
looks like it may be a good place for that given the process specific'ness
involved. The handler in that filter class could get the RPH and tell the
attached holder to ReleaseBlobReference(uuid).

wdyt?

[tommycli, 2014/05/23 16:27:44]

Actually that makes a lot of sense. I basically made those changes verbatim.

+ public:
+  virtual ~BlobHolder();
+
+  void HoldBlobReference(scoped_ptr<content::BlobHandle> blob);
+
+ private:
+  typedef ScopedVector<content::BlobHandle> BlobHandleVector;
+
+  explicit BlobHolder(content::WebContents* web_contents);
+  friend class content::WebContentsUserData<BlobHolder>;
+
+  bool ContainsBlobHandle(content::BlobHandle* handle) const;
+
+  // content::WebContentsObserver overrides.
+  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
+
+  // Message handlers.
+  void OnTransferBlobsAck(const std::vector<std::string>& blob_uuids);
+
+  BlobHandleVector held_blobs_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlobHolder);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_BLOB_HOLDER_H_