[screen-orientation] Update implementation to match recent spec changes.

Source/modules/screen_orientation/ScreenScreenOrientation.cpp

Index: Source/modules/screen_orientation/ScreenScreenOrientation.cpp
diff --git a/Source/modules/screen_orientation/ScreenScreenOrientation.cpp b/Source/modules/screen_orientation/ScreenScreenOrientation.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..db7537e20e9b3b2e800859bb5a078a4517b3460b
--- /dev/null
+++ b/Source/modules/screen_orientation/ScreenScreenOrientation.cpp
@@ -0,0 +1,53 @@
+// 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/screen_orientation/ScreenScreenOrientation.h"
+
+#include "bindings/core/v8/ScriptState.h"
+#include "core/frame/Screen.h"
+#include "modules/screen_orientation/ScreenOrientation.h"
+
+namespace WebCore {
+
+// static
+ScreenScreenOrientation& ScreenScreenOrientation::from(Screen& screen)
+{
+    ScreenScreenOrientation* supplement = static_cast<ScreenScreenOrientation*>(WillBeHeapSupplement<Screen>::from(screen, supplementName()));
+    if (!supplement) {
+        supplement = new ScreenScreenOrientation();
+        provideTo(screen, supplementName(), adoptPtrWillBeNoop(supplement));
+    }
+    return *supplement;
+}
+
+ScreenScreenOrientation::~ScreenScreenOrientation()
+{
+}
+
+// static
+ScreenOrientation* ScreenScreenOrientation::orientation(ScriptState* state, Screen& screen)
+{
+    ScreenScreenOrientation& self = ScreenScreenOrientation::from(screen);
+    if (!screen.frame())
+        return 0;
+
+    if (!self.m_orientation)
+        self.m_orientation = ScreenOrientation::create(screen.frame());
+
+    return self.m_orientation.get();
+}
+
+const char* ScreenScreenOrientation::supplementName()
+{
+    return "ScreenScreenOrientation";
+}
+
+void ScreenScreenOrientation::trace(Visitor* visitor)
+{
+    m_orientation->trace(visitor);

[sof, 2014/07/09 19:33:37]

Oh, this needs to be visitor->trace(m_orientation) as you want to mark the
ScreenOrientation via the visitor before later on tracing the actual object (if
not already marked.)

[sof, 2014/07/10 05:06:21]

It might be worth(re?)considering if the validation of trace() bodies could only
recognize trace() method calls of the above form. There might be some exceptions
(Persistents?) that don't fit, but I suspect not many.

[mlamouri (slow - plz ping), 2014/07/10 09:41:57]

Done.

+    WillBeHeapSupplement<Screen>::trace(visitor);
+}
+
+} // namespace WebCore