Support subtitles for native fullscreen video

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index ca69154269837eb9da2c96fe8b1737e383ef9467..2d4ef90336cd3670496718175e6089ef3fff081c 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -29,6 +29,7 @@
 
 #include "CSSPropertyNames.h"
 #include "HTMLNames.h"
+#include "RuntimeEnabledFeatures.h"
 #include "core/dom/NodeList.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/HTMLIFrameElement.h"
@@ -229,6 +230,7 @@ RenderLayerCompositor::RenderLayerCompositor(RenderView* renderView)
     , m_needsUpdateCompositingRequirementsState(false)
     , m_isTrackingRepaints(false)
     , m_rootLayerAttachment(RootLayerUnattached)
+    , m_currentFullscreenRenderer(0)
 #if !LOG_DISABLED
     , m_rootLayerUpdateCount(0)
     , m_obligateCompositedLayerCount(0)
@@ -446,6 +448,14 @@ void RenderLayerCompositor::updateCompositingLayers(CompositingUpdateType update
 
         // Host the document layer in the RenderView's root layer.
         if (isFullUpdate) {
+            if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && m_currentFullscreenRenderer && m_currentFullscreenRenderer->isMedia()) {
+                RenderLayerModelObject* renderer = toRenderLayerModelObject(m_currentFullscreenRenderer);

[esprehn, 2013/09/13 02:46:07]

SVG elements can never be full screen? They're not RenderLayerMOdelObjects so if
they can this doesn't seem safe.

[trchen, 2013/09/13 05:14:58]

This special code path only applies for RenderMedia. SVG elements use the usual
fullscreen code path.

+                RenderLayerBacking* backing = renderer->layer() ? renderer->layer()->backing() : 0;

[esprehn, 2013/09/13 02:46:07]

You should just add a method to RenderLayerModelObject like backing() and get
rid of the ternary here.

[trchen, 2013/09/13 05:14:58]

Done.

+                if (backing) {
+                    childList.clear();
+                    childList.append(backing->graphicsLayer());
+                }
+            }
             // Even when childList is empty, don't drop out of compositing mode if there are
             // composited layers that we didn't hit in our traversal (e.g. because of visibility:hidden).
             if (childList.isEmpty() && !hasAnyAdditionalCompositedLayers(updateRoot))
@@ -1835,6 +1845,9 @@ bool RenderLayerCompositor::requiresCompositingForTransform(RenderObject* render
 
 bool RenderLayerCompositor::requiresCompositingForVideo(RenderObject* renderer) const
 {
+    if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && renderer->isVideo() && renderer == m_currentFullscreenRenderer)
+        return true;
+
     if (!(m_compositingTriggers & ChromeClient::VideoTrigger))
         return false;
 
@@ -2761,4 +2774,13 @@ String RenderLayerCompositor::debugName(const GraphicsLayer* graphicsLayer)
     return name;
 }
 
+void RenderLayerCompositor::setCurrentFullscreenRenderer(RenderObject* renderer)
+{
+    if (renderer == m_currentFullscreenRenderer)
+        return;
+    m_currentFullscreenRenderer = renderer;

[esprehn, 2013/09/13 02:46:07]

I'm not a fan of keeping RenderObjects across frames or at all like this. I'd
rather you kept a RefPtr to a Node and called renderer() whenever you needed it.
That way you can never have a stale renderer.

[trchen, 2013/09/13 05:14:58]

That is one alternative way I have thought about. My concern is that it would be
a layer violation for the core/rendering to know anything about core/dom.
Actually I think keeping a RenderObject is safe. The only place we
construct/destruct render object is in Element::attach/detach, and I believe it
is guaranteed by design.

If in doubt, we can guard this code path with
REF::overlayFullscreenVideoEnabled() too, so we have some damage control if this
approach is in fact problematic.

+    if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled() && (!renderer || renderer->isVideo()))
+        setCompositingLayersNeedRebuild(true);
+}
+
 } // namespace WebCore