Fix resource leaks in CDM implementation.

ppapi/proxy/ppp_content_decryptor_private_proxy.cc

 // Copyright (c) 2012 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.
 
 #include "ppapi/proxy/ppp_content_decryptor_private_proxy.h"
 
 #include "base/platform_file.h"
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/ppb_core.h"
 #include "ppapi/proxy/content_decryptor_private_serializer.h"
@@ skipping 122 matching lines @@
     NOTREACHED();
     return PP_FALSE;
   }
   const PPB_Core* core = static_cast<const PPB_Core*>(
       dispatcher->local_get_interface()(PPB_CORE_INTERFACE));
   if (!core) {
     NOTREACHED();
     return PP_FALSE;
   }
 
-  // We need to take a ref on the resource now. The browser may drop
-  // references once we return from here, but we're sending an asynchronous
-  // message. The plugin side takes ownership of that reference.
-  core->AddRefResource(encrypted_block);

[dmichael (off chromium), 2012/09/05 18:08:37]

Okay, I think I had it wrong before. I was right that you *do* need this call.
That should make the renderer's reference count on the Buffer 2. When the caller
of Decrypt leaves, it should the reference count should go to 1. (I don't
remember off the top of my head which file that's in, but if it's not
decrementing the ref count, it should happen there).

The part I'm wrong about is that you shouldn't have to send a ReleaseResource
message back. The plugin side will assume that the host holds 1 reference count
on the resource. If the plugin-side ref-count goes to zero, then it will send
the ReleaseResource message on your behalf:
http://code.google.com/searchframe#OAMlx_jo-ck/src/ppapi/shared_impl/resource...

So if there's still a leak after checking the caller of Decrypt, then it's
probably because the plugin side is holding an extra reference.

Note that the ReleaseResource message is asynchronous (plugin->host), so the
resource won't go away until that message is received and handled in the
renderer.

[Tom Finegan, 2012/09/05 19:21:43]

Done.

-
   HostResource host_resource;
   host_resource.SetHostResource(instance, encrypted_block);
 
   uint32_t size = 0;
   if (DescribeHostBufferResource(encrypted_block, &size) == PP_FALSE)
     return PP_FALSE;
 
   base::SharedMemoryHandle handle;
   if (ShareHostBufferResourceToPlugin(dispatcher,
                                       encrypted_block,
@@ skipping 179 matching lines @@
       return;
     CallWhileUnlocked(ppp_decryptor_impl_->DecryptAndDecode,
                       instance,
                       plugin_resource,
                       const_cast<const PP_EncryptedBlockInfo*>(&block_info));
   }
 }
 
 }  // namespace proxy
 }  // namespace ppapi