Add media controls to MediaSession in Blink

third_party/WebKit/Source/modules/mediasession/MediaSession.cpp

Index: third_party/WebKit/Source/modules/mediasession/MediaSession.cpp
diff --git a/third_party/WebKit/Source/modules/mediasession/MediaSession.cpp b/third_party/WebKit/Source/modules/mediasession/MediaSession.cpp
index 9396d06843e9e67f71baaef9ee3d97071b653a36..0afbb0d8c1483b93121fc7f133fb10a5b3177c1b 100644
--- a/third_party/WebKit/Source/modules/mediasession/MediaSession.cpp
+++ b/third_party/WebKit/Source/modules/mediasession/MediaSession.cpp
@@ -8,6 +8,7 @@
 #include "core/dom/Document.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/frame/LocalFrame.h"
+#include "modules/EventTargetModules.h"
 #include "modules/mediasession/MediaMetadata.h"
 #include "modules/mediasession/MediaMetadataSanitizer.h"
 #include "public/platform/InterfaceProvider.h"
@@ -15,25 +16,33 @@
 
 namespace blink {
 
-MediaSession::MediaSession() = default;
+MediaSession::MediaSession(ScriptState* scriptState)
+    : m_scriptState(scriptState) {}
 
-MediaSession* MediaSession::create() {
-  return new MediaSession();
+MediaSession* MediaSession::create(ScriptState* scriptState) {
+  return new MediaSession(scriptState);
 }
 
-void MediaSession::setMetadata(ScriptState* scriptState,
-                               MediaMetadata* metadata) {
-  if (getService(scriptState)) {
-    getService(scriptState)
-        ->SetMetadata(
-            MediaMetadataSanitizer::sanitizeAndConvertToMojo(metadata));
+void MediaSession::setMetadata(MediaMetadata* metadata) {
+  if (mojom::blink::MediaSessionService* service =
+          getService(m_scriptState.get())) {
+    service->SetMetadata(
+        MediaMetadataSanitizer::sanitizeAndConvertToMojo(metadata));
   }
 }
 
-MediaMetadata* MediaSession::metadata(ScriptState*) const {
+MediaMetadata* MediaSession::metadata() const {
   return m_metadata;
 }
 
+const WTF::AtomicString& MediaSession::interfaceName() const {
+  return EventTargetNames::MediaSession;
+}
+
+ExecutionContext* MediaSession::getExecutionContext() const {
+  return m_scriptState->getExecutionContext();
+}
+
 mojom::blink::MediaSessionService* MediaSession::getService(
     ScriptState* scriptState) {
   if (!m_service) {
@@ -50,8 +59,27 @@ mojom::blink::MediaSessionService* MediaSession::getService(
   return m_service.get();
 }
 
+bool MediaSession::addEventListenerInternal(
+    const AtomicString& eventType,
+    EventListener* listener,
+    const AddEventListenerOptionsResolved& options) {
+  // TODO(zqzhang): Notify MediaSessionService the handler has been set. See

[foolip, 2016/10/19 13:35:45]

Not sure what MediaSessionService will do, but guessing that it'll affect what
bits of UI are visible.

Since there's no hasEventListener(), this is something that web developers can't
do, and there's currently no spec language one can use to do the same thing.
This is intentional, as it would mean that adding event listeners could change
behavior. (There are already cases where this happens, like when prefixed events
fire only if there were no event handlers for the unprefixed one, but none of
this has been enshrined in a spec yet.)

Some mechanism like .showTheseThings(['play', 'rewind', 'star']) might be
necessary. Since these overrides don't do anything yet, I'd suggest dropping
them, and if I'm just wrong you can add them when you need them.

[Zhiqiang Zhang (Slow), 2016/10/19 14:54:05]

Yes, there are some arguments on the API about this, but we haven't decided yet.

+  // https://crbug.com/656563
+  return EventTarget::addEventListenerInternal(eventType, listener, options);
+}
+
+bool MediaSession::removeEventListenerInternal(
+    const AtomicString& eventType,
+    const EventListener* listener,
+    const EventListenerOptions& options) {
+  // TODO(zqzhang): Notify MediaSessionService the handler has been unset. See
+  // https://crbug.com/656563
+  return EventTarget::removeEventListenerInternal(eventType, listener, options);
+}
+
 DEFINE_TRACE(MediaSession) {
   visitor->trace(m_metadata);
+  EventTargetWithInlineData::trace(visitor);
 }
 
 }  // namespace blink