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..326e3aa9c100ec478554e1b92c378f2dace39536 100644
--- a/third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp
+++ b/third_party/WebKit/Source/core/dom/ElementVisibilityObserver.cpp
@@ -21,12 +21,34 @@ bool isInRemoteFrame(const Document& document) {
 
 }  // anonymous namespace
 
+VisibilityObserverBase::VisibilityObserverBase(Element* element)
+    : m_element(element) {}
+
+VisibilityObserverBase::~VisibilityObserverBase() {}
+
+void VisibilityObserverBase::stop() {
+  // TODO(zqzhang): IntersectionObserver does not work for RemoteFrame,
+  // so |m_intersectionObserver| may be null at this point after start().
+  // Replace this early return with DCHECK when this has been fixed. See
+  // https://crbug.com/615156
+  if (!m_intersectionObserver)
+    return;
+
+  m_intersectionObserver->disconnect();
+  m_intersectionObserver = nullptr;
+}
+
+DEFINE_TRACE(VisibilityObserverBase) {
+  visitor->trace(m_element);
+  visitor->trace(m_intersectionObserver);
+}
+
 ElementVisibilityObserver::ElementVisibilityObserver(
     Element* element,
     std::unique_ptr<VisibilityCallback> callback)
-    : m_element(element), m_callback(std::move(callback)) {}
+    : VisibilityObserverBase(element), m_callback(std::move(callback)) {}
 
-ElementVisibilityObserver::~ElementVisibilityObserver() = default;
+ElementVisibilityObserver::~ElementVisibilityObserver() {}
 
 void ElementVisibilityObserver::start() {
   ExecutionContext* context = m_element->getExecutionContext();
@@ -51,31 +73,49 @@ void ElementVisibilityObserver::start() {
   m_intersectionObserver->observe(m_element.release());
 }
 
-void ElementVisibilityObserver::stop() {
-  // TODO(zqzhang): IntersectionObserver does not work for RemoteFrame,
-  // so |m_intersectionObserver| may be null at this point after start().
-  // Replace this early return with DCHECK when this has been fixed. See
-  // https://crbug.com/615156
-  if (!m_intersectionObserver)
-    return;
-
-  m_intersectionObserver->disconnect();
-  m_intersectionObserver = nullptr;
-}
-
 void ElementVisibilityObserver::deliverObservationsForTesting() {
   m_intersectionObserver->deliver();
 }
 
-DEFINE_TRACE(ElementVisibilityObserver) {
-  visitor->trace(m_element);
-  visitor->trace(m_intersectionObserver);
-}
-
 void ElementVisibilityObserver::onVisibilityChanged(
     const HeapVector<Member<IntersectionObserverEntry>>& entries) {
   bool isVisible = entries.last()->intersectionRatio() > 0.f;
   (*m_callback.get())(isVisible);
 }
 
+ElementViewportRatioObserver::ElementViewportRatioObserver(
+    Element* element,
+    std::unique_ptr<RatioChangeCallback> callback)
+    : VisibilityObserverBase(element), m_callback(std::move(callback)) {}
+
+ElementViewportRatioObserver::~ElementViewportRatioObserver() {}
+
+void ElementViewportRatioObserver::start() {
+  ExecutionContext* context = m_element->getExecutionContext();
+  DCHECK(context->isDocument());
+  Document& document = toDocument(*context);
+
+  // TODO(zqzhang): IntersectionObserver does not work for RemoteFrame.
+  // Remove this early return when it's fixed. See https://crbug.com/615156
+  if (isInRemoteFrame(document)) {
+    m_element.release();
+    return;
+  }
+
+  DCHECK(!m_intersectionObserver);
+  m_intersectionObserver = IntersectionObserver::create(
+      Vector<Length>(), &document,
+      WTF::bind(&ElementViewportRatioObserver::onVisibilityChanged,
+                wrapWeakPersistent(this)));
+  DCHECK(m_intersectionObserver);
+  m_intersectionObserver->setInitialState(
+      IntersectionObserver::InitialState::kAuto);
+  m_intersectionObserver->observe(m_element.release());
+}
+
+void ElementViewportRatioObserver::onVisibilityChanged(
+    const HeapVector<Member<IntersectionObserverEntry>>& entries) {
+  (*m_callback.get())(entries.last()->intersectionRatio());
+}
+
 }  // namespace blink