Monitor the intersection of video and viewport.

third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp

Index: third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp
diff --git a/third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp b/third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp
index 8c4ecab9c24d74549216268dbf9a3f38e3310e9a..4160f7bdda303b9df15414895e2cd67f7e18276e 100644
--- a/third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp
+++ b/third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp
@@ -29,6 +29,15 @@ ElementVisibilityObserver::ElementVisibilityObserver(
 ElementVisibilityObserver::~ElementVisibilityObserver() = default;
 
 void ElementVisibilityObserver::start() {
+  startInternal(false);
+}
+
+void ElementVisibilityObserver::startObserveElementViewportRatio() {
+  startInternal(true);
+}
+
+void ElementVisibilityObserver::startInternal(
+    bool isObservingElementViewportRatio) {
   ExecutionContext* context = m_element->getExecutionContext();
   DCHECK(context->isDocument());
   Document& document = toDocument(*context);
@@ -41,10 +50,17 @@ void ElementVisibilityObserver::start() {
   }
 
   DCHECK(!m_intersectionObserver);
-  m_intersectionObserver = IntersectionObserver::create(
-      Vector<Length>(), Vector<float>({std::numeric_limits<float>::min()}),
-      &document, WTF::bind(&ElementVisibilityObserver::onVisibilityChanged,
-                           wrapWeakPersistent(this)));
+  if (isObservingElementViewportRatio) {
+    m_intersectionObserver = IntersectionObserver::create(
+        Vector<Length>(), &document,
+        WTF::bind(&ElementVisibilityObserver::onVisibilityChanged,
+                  wrapWeakPersistent(this)));
+  } else {
+    m_intersectionObserver = IntersectionObserver::create(
+        Vector<Length>(), Vector<float>({std::numeric_limits<float>::min()}),
+        &document, WTF::bind(&ElementVisibilityObserver::onVisibilityChanged,
+                             wrapWeakPersistent(this)));
+  }
   DCHECK(m_intersectionObserver);
   m_intersectionObserver->setInitialState(
       IntersectionObserver::InitialState::kAuto);
@@ -74,8 +90,17 @@ DEFINE_TRACE(ElementVisibilityObserver) {
 
 void ElementVisibilityObserver::onVisibilityChanged(
     const HeapVector<Member<IntersectionObserverEntry>>& entries) {
-  bool isVisible = entries.last()->intersectionRatio() > 0.f;
-  (*m_callback.get())(isVisible);
+  m_ratio = entries.last()->intersectionRatio();
+  (*m_callback.get())(m_ratio > 0.f);
+}
+
+ElementViewportRatioObserver::ElementViewportRatioObserver(
+    Element* element,
+    std::unique_ptr<VisibilityCallback> callback)
+    : ElementVisibilityObserver(element, std::move(callback)) {}
+
+void ElementViewportRatioObserver::start() {
+  startObserveElementViewportRatio();
 }
 
 }  // namespace blink