Add PPAPI decryptor interfaces.

ppapi/api/dev/ppp_content_decryption_module_dev.idl

+/* 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.
+ */
+
+/**
+ * This file defines the <code>PPP_ContentDecryptionModule_Dev</code>
+ * interface.
+ */
+label Chrome {
+  M22 = 0.1
+};
+
+/**
+ * <code>PPP_ContentDecryptionModule_Dev</code> structure contains the function
+ * pointers the decryption plugin MUST implement to provide services needed by
+ * the media stack.
+ */
+interface PPP_ContentDecryptionModule_Dev {
+  /**
+   * Provides a key or license to use for decryption. The key determines
+   * which methods are allowed by the plugin.
+   */

[ddorwin, 2012/06/06 21:52:52]

We'll need GenerateKeyRequest() relatively soon and eventually something like
CancelKeyRequest().

We'll probably want to provide the key system name in case a single CDM
implements multiple key system variations.

[Tom Finegan, 2012/06/07 00:50:50]

How about:

  PP_Bool GenerateKeyRequest(
    [in] PP_Instance instance,
    [in] PP_CompletionCallback callback);

  PP_Bool CancelKeyRequest(
    [in] PP_Instance instance);

[ddorwin, 2012/06/07 18:51:26]

Need key_system and init_data.
Need session_id

+  PP_Bool AddKey(
+      [in] PP_Instance instance,
+      [in] PP_Resource key);
+
+  /**
+   * Decrypts the block and returns the unencrypted block.
+   * In the case of media, the block contains encoded data.
+   * decryptedBlock is valid only after the callback is notified of success.

[ddorwin, 2012/06/06 21:52:52]

Argument names in comments do not match the arguments.

[Tom Finegan, 2012/06/07 00:50:50]

Done.

+   */
+  PP_Bool Decrypt(
+      [in] PP_Instance instance,
+      [in] PP_Resource encrypted_block,
+      [in] PP_Resource decrypted_block,
+      [in] PP_CompletionCallback callback);

[ddorwin, 2012/06/06 21:52:52]

I wonder how we can report API-specific errors, such as those in MediaKeyError
(or systemCode). Maybe user_data in the callback will need to be a structure
with this data. We can add this later if necessary, I guess.

[Tom Finegan, 2012/06/07 00:50:50]

Yeah, I think that's what we'll have to do if we want to use
PP_CompletionCallback as-is. Where would the struct end up getting defined-- is
there something similar I can look at to get a head start on adding the error
reporting? It should probably be in there from the start.

[ddorwin, 2012/06/07 18:51:26]

I'm not sure if anyone actually does this. I think the general usage is to pass
data to yourself (the same side of the API). Thus, the browser could have the
plugin pass data back to it or vice versa. This use case would require both
sides to modify/read the data structure.

I noticed that some PPP APIs have corresponding PPB APIs that provide callbacks.
That's another option, though it's more complex. It might actually be necessary
unless the decoded_frame PPB_Buffer can be resized by the plugin.

+
+  /**
+   * Decrypts the block then decodes it and returns the raw (decoded)
+   * unencrypted frame.
+   * decodedFrame is valid only after the callback is notified of success.
+   */
+  PP_Bool DecryptAndDecode(

[ddorwin, 2012/06/06 21:52:52]

We're going to need to somehow provide codec information, etc. I guess we can
figure that out.

+      [in] PP_Instance instance,
+      [in] PP_Resource encrypted_block,
+      [in] PP_Resource decoded_frame,
+      [in] PP_CompletionCallback callback);
+};