Implement navigator.requestMediaKeySystemAccess()

Source/modules/encryptedmedia/MediaKeySystemAccess.cpp

+// 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.
+
+#include "config.h"
+#include "modules/encryptedmedia/MediaKeySystemAccess.h"
+
+#include "bindings/core/v8/ScriptPromiseResolver.h"
+#include "bindings/core/v8/ScriptState.h"
+#include "core/dom/DOMException.h"
+#include "core/dom/Document.h"
+#include "core/dom/ExceptionCode.h"
+#include "modules/encryptedmedia/MediaKeys.h"
+#include "modules/encryptedmedia/MediaKeysController.h"
+#include "platform/Logging.h"
+#include "platform/Timer.h"
+#include "public/platform/WebContentDecryptionModule.h"
+
+namespace blink {
+
+// This class allows a MediaKeys object to be created asynchronously.

[yhirano, 2014/10/24 09:22:32]

Can you place this class in an unnamed namespace?

[jrummell, 2014/10/24 22:43:22]

Only by removing the logging. Done.

+class MediaKeysInitializer : public ScriptPromiseResolver {

[haraken, 2014/10/24 01:06:42]

Add final.

[jrummell, 2014/10/24 22:43:22]

Done.

+    WTF_MAKE_NONCOPYABLE(MediaKeysInitializer);
+
+public:
+    static ScriptPromise create(ScriptState*, const String& keySystem);
+    virtual ~MediaKeysInitializer();
+
+private:
+    MediaKeysInitializer(ScriptState*, const String& keySystem);
+    void timerFired(Timer<MediaKeysInitializer>*);
+
+    const String m_keySystem;
+    Timer<MediaKeysInitializer> m_timer;
+};
+
+ScriptPromise MediaKeysInitializer::create(ScriptState* scriptState, const String& keySystem)
+{
+    RefPtr<MediaKeysInitializer> initializer = adoptRef(new MediaKeysInitializer(scriptState, keySystem));
+    initializer->suspendIfNeeded();
+    initializer->keepAliveWhilePending();
+    return initializer->promise();
+}
+
+MediaKeysInitializer::MediaKeysInitializer(ScriptState* scriptState, const String& keySystem)
+    : ScriptPromiseResolver(scriptState)
+    , m_keySystem(keySystem)
+    , m_timer(this, &MediaKeysInitializer::timerFired)
+{
+    WTF_LOG(Media, "MediaKeysInitializer::MediaKeysInitializer");
+    // Start the timer so that MediaKeys can be created asynchronously.

[yhirano, 2014/10/24 09:22:32]

I'm sorry if this is the second time, but can you tell me why you want to create
MediaKeys asynchronously? Even if you create it synchronously (in terms of blink
C++), fulfill / reject handlers will be called asynchronously (in the JS world).

[jrummell, 2014/10/24 22:43:22]

createContentDecryptionModule() may require the CDM to be loaded, which is why
we don't want to run synchronously.

[yhirano, 2014/10/27 02:26:28]

Sorry I still don't understand...
1) What do you mean by "may"? I checked layout tests passed even when I remove
this timer.
2) If you are waiting for an event ("CDM gets loaded"?) here, is it guaranteed
that it's done when the timer fires? How?

[jrummell, 2014/10/27 21:23:28]

The layout tests all use ClearKey CDM, which is built in to Chrome (thus nothing
to load). Most applications (e.g YouTube encrypted content) will use WideVine
CDM, which is loaded like a plug-in.

createContentDecryptionModule() currently runs synchronously, so there is no
"CDM gets loaded" event.

Right now, I'm just trying to follow the current spec
(https://dvcs.w3.org/hg/html-media/raw-file/default/encrypted-media/encrypted-...).

[yhirano, 2014/10/28 02:02:01]

OK, then please write a comment describing that here (and in
NavigatorRequestMediaKeySystemAccess.cpp).
When createContentDecryptionModule gets asynchronous, you will have to wait for
the event, not a timer event, right? If so, please write so as well.

[jrummell, 2014/10/28 17:45:44]

Done.

[yhirano, 2014/10/29 01:44:26]

As wrote above, please write in NavigatorRequestMediaKeySystemAccess.cpp, too.

[jrummell, 2014/10/29 18:24:43]

Done.

+    m_timer.startOneShot(0, FROM_HERE);
+}
+
+MediaKeysInitializer::~MediaKeysInitializer()
+{
+    WTF_LOG(Media, "MediaKeysInitializer::~MediaKeysInitializer");
+}
+
+void MediaKeysInitializer::timerFired(Timer<MediaKeysInitializer>*)
+{
+    WTF_LOG(Media, "MediaKeysInitializer::timerFired");
+
+    // NOTE: Continued from step 2. of MediaKeySystemAccess::createMediaKeys().
+    // 2.1 Let cdm be the CDM corresponding to this object.
+    // 2.2 Load and initialize the cdm if necessary.
+    Document* document = toDocument(executionContext());
+    MediaKeysController* controller = MediaKeysController::from(document->page());
+    // FIXME: Should this return an error code so there can be a better error
+    // message than UnknownError? Should it be asynchronous (maybe use
+    // webContentDecryptionModuleResult)?
+    OwnPtr<WebContentDecryptionModule> cdm = controller->createContentDecryptionModule(executionContext(), m_keySystem);
+
+    // 2.3 If cdm fails to load or initialize, reject promise with a new
+    //     DOMException whose name is the appropriate error name.
+    if (!cdm) {
+        String message("A CDM instance could not be created for the '" + m_keySystem + "' key system.");
+        reject(DOMException::create(UnknownError, message));
+        return;
+    }
+
+    // 2.4 Let media keys be a new MediaKeys object.
+    MediaKeys* mediaKeys = new MediaKeys(executionContext(), m_keySystem, cdm.release());
+
+    // 2.5 Resolve promise with media keys.
+    resolve(mediaKeys);
+
+    // Note: As soon as the promise is resolved (or rejected), the
+    // ScriptPromiseResolver object (|this|) is freed. So access to
+    // any members will crash once the promise is fulfilled.
+}
+
+MediaKeySystemAccess::MediaKeySystemAccess(const String& keySystem)
+    : m_keySystem(keySystem)
+{
+    // FIXME: There should be a Chromium-side equivalent object that contains
+    // any information, including the key system, from the results of the
+    // request call. It would also give us a place to put the createCDM() call.
+}
+
+MediaKeySystemAccess::~MediaKeySystemAccess()
+{
+}
+
+ScriptPromise MediaKeySystemAccess::createMediaKeys(ScriptState* scriptState)
+{
+    // From https://dvcs.w3.org/hg/html-media/raw-file/default/encrypted-media/encrypted-media.html#widl-MediaKeySystemAccess-createMediaKeys-Promise-MediaKeys
+    // When this method is invoked, the user agent must run the following steps:
+    // 1. Let promise be a new promise.
+    // 2. Asynchronously create and initialize the MediaKeys object.
+    // 3. Return promise.
+    return MediaKeysInitializer::create(scriptState, m_keySystem);
+}
+
+void MediaKeySystemAccess::trace(Visitor*)
+{
+}
+
+} // namespace blink