Intersection Observer first draft

Source/core/frame/FrameView.cpp

Index: Source/core/frame/FrameView.cpp
diff --git a/Source/core/frame/FrameView.cpp b/Source/core/frame/FrameView.cpp
index e4635d9f6241e3ebe2688d4f991e65c383eaba5e..cbcf6e38a466efee450c3744bb561a0db35f7acd 100644
--- a/Source/core/frame/FrameView.cpp
+++ b/Source/core/frame/FrameView.cpp
@@ -1116,6 +1116,28 @@ void FrameView::invalidateTreeIfNeeded(PaintInvalidationState& paintInvalidation
 
     m_doFullPaintInvalidation = false;
     lifecycle().advanceTo(DocumentLifecycle::PaintInvalidationClean);
+
+    if (RuntimeEnabledFeatures::intersectionObserverEnabled()) {
+        computeIntersectionObservations(paintInvalidationState);
+    }
+}
+
+void FrameView::computeIntersectionObservations(PaintInvalidationState& paintInvalidationState)
+{
+    ASSERT(layoutView());
+
+    if (FrameView* parent = parentFrameView()) {

[ojan, 2015/09/21 03:49:09]

Does this handle clipping correctly if you have multiple levels of nested
frames?

+        m_clippedBounds = IntRect(frameRect().location(), paintInvalidationState.clipRect().pixelSnappedSize());
+        m_clippedBounds = parent->contentsToRootFrame(m_clippedBounds);
+        m_clippedBounds.intersect(parent->contentsToRootFrame(parent->m_clippedBounds));
+        if (!m_clippedBounds.isEmpty()) {

[ojan, 2015/09/21 03:49:09]

Nit: no curlies

[MikeB, 2015/09/24 19:04:04]

Done.

+            m_clippedBounds = rootFrameToContents(m_clippedBounds);
+        }
+    } else {
+        m_clippedBounds = pixelSnappedIntRect(paintInvalidationState.clipRect());
+    }
+
+    layoutView()->computeIntersectionObservations(FloatRect(m_clippedBounds));
 }
 
 DocumentLifecycle& FrameView::lifecycle() const