[IntersectionObserver] Report coordinates as CSS pixels.

Prior to this patch, IntersectionObserverEntry was reporting
coordinates in device pixels.

BUG=887974

Change-Id: Ic91748cd2eb9b828a787bb4372d5d5b10bcf8cfb
Reviewed-on: https://chromium-review.googlesource.com/1250121
Commit-Queue: Stefan Zager <szager@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595190}

third_party/WebKit/LayoutTests/external/wpt/intersection-observer/bounding-box.html

@@ -13,7 +13,7 @@ pre, #log {
   overflow: visible;
   height: 200px;
   width: 160px;
-  border: 7px solid black;
+  border: 8px solid black;
 }
 #target {
   margin: 10px;
@@ -50,12 +50,35 @@ function step0() {
   var targetBounds = clientBounds(target);
   target.style.transform = "translateY(195px)";
   runTestCycle(step1, "target.style.transform = 'translateY(195px)'");
-  checkLastEntry(entries, 0, targetBounds.concat(0, 0, 0, 0, 8, 182, 8, 222, false));
+  checkLastEntry(entries, 0, targetBounds.concat(0, 0, 0, 0, 8, 184, 8, 224, false));
 }
 
 function step1() {
+  var targetBounds = clientBounds(target);
+  target.style.transform = "translateY(300px)";
+  runTestCycle(step2, "target.style.transform = 'translateY(300px)'");
+  checkLastEntry(entries, 1, targetBounds.concat(26, 146, 221, 224, 8, 184, 8, 224, true));
+}
+
+function step2() {
   var targetBounds = clientBounds(target);
   target.style.transform = "";
-  checkLastEntry(entries, 1, targetBounds.concat(25, 145, 220, 222, 8, 182, 8, 222, true));
+  target.style.zoom = "2";
+  runTestCycle(step3, "target.style.zoom = 2");
+  checkLastEntry(entries, 2, targetBounds.concat(0, 0, 0, 0, 8, 184, 8, 224, false));
 }
+
+function step3() {
+  var targetBounds = clientBounds(target);
+  var intersectionWidth = (
+      176  // root width including border
+      -8   // root left border
+      -20  // target left margin * target zoom
+  ) / 2;   // convert to target's zoom factor.
+  var intersectionHeight = (216 - 8 - 20) / 2;
+  var intersectionRect = [targetBounds[0], targetBounds[0] + intersectionWidth,
+                          targetBounds[2], targetBounds[2] + intersectionHeight];
+  checkLastEntry(entries, 3, targetBounds.concat(intersectionRect).concat(8, 184, 8, 224, true));
+}
+
 </script>

third_party/blink/renderer/core/intersection_observer/intersection_observation.cc

@@ -120,12 +120,12 @@ void IntersectionObservation::Compute(unsigned flags) {
 
   if (last_threshold_index_ != new_threshold_index ||
       last_is_visible_ != is_visible) {
-    FloatRect snapped_root_bounds(geometry.RootRect());
+    FloatRect root_bounds(geometry.UnZoomedRootRect());
     FloatRect* root_bounds_pointer =
-        report_root_bounds ? &snapped_root_bounds : nullptr;
+        report_root_bounds ? &root_bounds : nullptr;
     IntersectionObserverEntry* new_entry = new IntersectionObserverEntry(
-        timestamp, new_visible_ratio, FloatRect(geometry.TargetRect()),
-        root_bounds_pointer, FloatRect(geometry.IntersectionRect()),
+        timestamp, new_visible_ratio, FloatRect(geometry.UnZoomedTargetRect()),
+        root_bounds_pointer, FloatRect(geometry.UnZoomedIntersectionRect()),
         new_threshold_index > 0, is_visible, Target());
     entries_.push_back(new_entry);
     ToDocument(Observer()->GetExecutionContext())

third_party/blink/renderer/core/layout/intersection_geometry.cc

@@ -8,6 +8,7 @@
 #include "third_party/blink/renderer/core/frame/local_frame_view.h"
 #include "third_party/blink/renderer/core/frame/settings.h"
 #include "third_party/blink/renderer/core/html/html_frame_owner_element.h"
+#include "third_party/blink/renderer/core/layout/adjust_for_absolute_zoom.h"
 #include "third_party/blink/renderer/core/layout/layout_box.h"
 #include "third_party/blink/renderer/core/layout/layout_inline.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
@@ -233,4 +234,28 @@ void IntersectionGeometry::ComputeGeometry() {
     MapRootRectToRootFrameCoordinates();
 }
 
+LayoutRect IntersectionGeometry::UnZoomedTargetRect() const {
+  if (!target_)
+    return target_rect_;
+  FloatRect rect(target_rect_);
+  AdjustForAbsoluteZoom::AdjustFloatRect(rect, *target_);
+  return LayoutRect(rect);
+}
+
+LayoutRect IntersectionGeometry::UnZoomedIntersectionRect() const {
+  if (!target_)
+    return intersection_rect_;
+  FloatRect rect(intersection_rect_);
+  AdjustForAbsoluteZoom::AdjustFloatRect(rect, *target_);
+  return LayoutRect(rect);
+}
+
+LayoutRect IntersectionGeometry::UnZoomedRootRect() const {
+  if (!root_)
+    return root_rect_;
+  FloatRect rect(root_rect_);
+  AdjustForAbsoluteZoom::AdjustFloatRect(rect, *root_);
+  return LayoutRect(rect);
+}
+
 }  // namespace blink

third_party/blink/renderer/core/layout/intersection_geometry.h

@@ -38,12 +38,18 @@ class IntersectionGeometry {
 
   // Client rect in the coordinate system of the frame containing target.
   LayoutRect TargetRect() const { return target_rect_; }
+  // Target rect in CSS pixels
+  LayoutRect UnZoomedTargetRect() const;
 
   // Client rect in the coordinate system of the frame containing target.
   LayoutRect IntersectionRect() const { return intersection_rect_; }
+  // Intersection rect in CSS pixels
+  LayoutRect UnZoomedIntersectionRect() const;
 
   // Client rect in the coordinate system of the frame containing root.
   LayoutRect RootRect() const { return root_rect_; }
+  // Root rect in CSS pixels
+  LayoutRect UnZoomedRootRect() const;
 
   bool DoesIntersect() const { return does_intersect_; }