IntersectionObserver: use edge-inclusive geometry for intersections.

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 847b288ad50159636e8b905ad715a5879a417280..dac0764a9d9b2566dd22bcdbdcdc0221bbb91926 100644
--- a/third_party/WebKit/Source/core/dom/IntersectionObserver.cpp
+++ b/third_party/WebKit/Source/core/dom/IntersectionObserver.cpp
@@ -290,13 +290,6 @@ void IntersectionObserver::applyRootMargin(LayoutRect& rect) const
 unsigned IntersectionObserver::firstThresholdGreaterThan(float ratio) const
 {
     unsigned result = 0;
-
-    // Special handling for zero threshold, which means "any non-zero number of pixels."
-    // If the ratio is zero, then it should be treated as smaller than any threshold,
-    // even a zero threshold.
-    if (!ratio)
-        return 0;
-
     while (result < m_thresholds.size() && m_thresholds[result] <= ratio)
         ++result;
     return result;