Monitor the intersection of video and viewport.

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

Index: third_party/WebKit/Source/core/dom/IntersectionObserver.cpp
diff --git a/third_party/WebKit/Source/core/dom/IntersectionObserver.cpp b/third_party/WebKit/Source/core/dom/IntersectionObserver.cpp
index 32ef04c78978b5f0856a4812c1ff8499585d1e5d..6602688036bf32fdb795e33eb975e2c2c39e2041 100644
--- a/third_party/WebKit/Source/core/dom/IntersectionObserver.cpp
+++ b/third_party/WebKit/Source/core/dom/IntersectionObserver.cpp
@@ -169,7 +169,8 @@ IntersectionObserver* IntersectionObserver::create(
   if (exceptionState.hadException())
     return nullptr;
 
-  return new IntersectionObserver(callback, *root, rootMargin, thresholds);
+  return new IntersectionObserver(callback, *root, rootMargin, thresholds,
+                                  false);
 }
 
 IntersectionObserver* IntersectionObserver::create(
@@ -189,14 +190,34 @@ IntersectionObserver* IntersectionObserver::create(
   IntersectionObserverCallbackImpl* intersectionObserverCallback =
       new IntersectionObserverCallbackImpl(document, std::move(callback));
   return new IntersectionObserver(*intersectionObserverCallback, *root,
-                                  rootMargin, thresholds);
+                                  rootMargin, thresholds, false);
+}
+
+IntersectionObserver* IntersectionObserver::create(

[miu, 2016/11/09 22:02:08]

Get rid of the special-case boolean (see comments below). Then, you don't need
this extra create() function. (The one above can be called with an empty set of
|thresholds|.)

[xjz, 2016/11/11 01:07:29]

Keeps the boolean to indicate observing element/viewport ratio. I am not sure if
this create() can be saved though. If the IntersectionObserver always asking for
a non-empty thresholds vector, we can use an empty thresholds vector to indicate
observing element/viewport ratio, and saved this create(). 

+ojan

+    const Vector<Length>& rootMargin,
+    Document* document,
+    std::unique_ptr<EventCallback> callback,
+    ExceptionState& exceptionState) {
+  Node* root = getRootNode(document);
+  if (!root) {
+    exceptionState.throwDOMException(
+        HierarchyRequestError,
+        "Unable to get root node in main frame to track.");
+    return nullptr;
+  }
+
+  IntersectionObserverCallbackImpl* intersectionObserverCallback =
+      new IntersectionObserverCallbackImpl(document, std::move(callback));
+  return new IntersectionObserver(*intersectionObserverCallback, *root,
+                                  rootMargin, Vector<float>(), true);
 }
 
 IntersectionObserver::IntersectionObserver(
     IntersectionObserverCallback& callback,
     Node& root,
     const Vector<Length>& rootMargin,
-    const Vector<float>& thresholds)
+    const Vector<float>& thresholds,
+    bool isObservingRatio)
     : m_callback(&callback),
       m_root(&root),
       m_thresholds(thresholds),
@@ -204,7 +225,8 @@ IntersectionObserver::IntersectionObserver(
       m_rightMargin(Fixed),
       m_bottomMargin(Fixed),
       m_leftMargin(Fixed),
-      m_initialState(InitialState::kHidden) {
+      m_initialState(InitialState::kHidden),
+      m_observeElementViewportRatio(isObservingRatio) {
   switch (rootMargin.size()) {
     case 0:
       break;
@@ -269,7 +291,9 @@ void IntersectionObserver::observe(Element* target,
   LocalFrame* targetFrame = target->document().frame();
   LocalFrame* rootFrame = m_root->document().frame();
 
-  if (target->document() == rootNode()->document()) {
+  if (m_observeElementViewportRatio) {

[miu, 2016/11/09 22:02:08]

Please get rid of this extra boolean. Instead, the caller of this observe()
method should provide a |target| that is equal to the rootNode().

[xjz, 2016/11/11 01:07:29]

As discussed offline, the |target| is the video element, and the root is the
viewport. keeps the boolean.

+    shouldReportRootBounds = true;
+  } else if (target->document() == rootNode()->document()) {
     shouldReportRootBounds = true;
     isDOMDescendant = rootNode()->isShadowIncludingInclusiveAncestorOf(target);
   } else if (targetFrame && rootFrame) {