[IntersectionObserver] Don't snap bounding rects

These rects should mirror the behavior of getBoundingClientRect,
which doesn't snap.

BUG=758587,737228

Change-Id: If735df6bd24414dfbbd58dce01dc2a90f71df381
Reviewed-on: https://chromium-review.googlesource.com/951640Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542548}

third_party/WebKit/LayoutTests/intersection-observer/client-rect.html

@@ -15,7 +15,7 @@ iframe {
 }
 </style>
 
-<iframe id="iframe" srcdoc="<div id='target' style='width:1000px;height:1000px;'></div>"></iframe>
+<iframe id="iframe" srcdoc="<div id='target' style='margin:0.5px;width:1000px;height:1000px;'></div>"></iframe>
 
 <script>
 var target;
@@ -37,7 +37,7 @@ iframe.onload = function() {
     entries = entries.concat(observer.takeRecords());
     assert_equals(entries.length, 0, "No initial notifications.");
     runTestCycle(test0, "First rAF should generate notification.");
-  }, "IntersectionObserverEntry.boundingClientRect should match target.boundingClientRect()");
+  }, "IntersectionObserverEntry.boundingClientRect should match target.getBoundingClientRect()");
 };
 
 function test0() {

third_party/WebKit/Source/core/intersection_observer/IntersectionObservation.cpp

@@ -73,12 +73,12 @@ void IntersectionObservation::ComputeIntersectionObservations(
   CHECK(new_threshold_index < kMaxThresholdIndex);
 
   if (last_threshold_index_ != new_threshold_index) {
-    IntRect snapped_root_bounds = geometry.RootIntRect();
-    IntRect* root_bounds_pointer =
+    FloatRect snapped_root_bounds(geometry.RootRect());
+    FloatRect* root_bounds_pointer =
         should_report_root_bounds_ ? &snapped_root_bounds : nullptr;
     IntersectionObserverEntry* new_entry = new IntersectionObserverEntry(
-        timestamp, new_visible_ratio, geometry.TargetIntRect(),
-        root_bounds_pointer, geometry.IntersectionIntRect(),
+        timestamp, new_visible_ratio, FloatRect(geometry.TargetRect()),
+        root_bounds_pointer, FloatRect(geometry.IntersectionRect()),
         geometry.DoesIntersect(), Target());
     Observer()->EnqueueIntersectionObserverEntry(*new_entry);
     SetLastThresholdIndex(new_threshold_index);

third_party/WebKit/Source/core/intersection_observer/IntersectionObserverEntry.cpp

@@ -11,17 +11,18 @@ namespace blink {
 IntersectionObserverEntry::IntersectionObserverEntry(
     DOMHighResTimeStamp time,
     double intersection_ratio,
-    const IntRect& bounding_client_rect,
-    const IntRect* root_bounds,
-    const IntRect& intersection_rect,
+    const FloatRect& bounding_client_rect,
+    const FloatRect* root_bounds,
+    const FloatRect& intersection_rect,
     bool is_intersecting,
     Element* target)
     : time_(time),
       intersection_ratio_(intersection_ratio),
-      bounding_client_rect_(DOMRectReadOnly::FromIntRect(bounding_client_rect)),
-      root_bounds_(root_bounds ? DOMRectReadOnly::FromIntRect(*root_bounds)
+      bounding_client_rect_(
+          DOMRectReadOnly::FromFloatRect(bounding_client_rect)),
+      root_bounds_(root_bounds ? DOMRectReadOnly::FromFloatRect(*root_bounds)
                                : nullptr),
-      intersection_rect_(DOMRectReadOnly::FromIntRect(intersection_rect)),
+      intersection_rect_(DOMRectReadOnly::FromFloatRect(intersection_rect)),
       target_(target),
       is_intersecting_(is_intersecting)
 

third_party/WebKit/Source/core/intersection_observer/IntersectionObserverEntry.h

@@ -21,9 +21,9 @@ class IntersectionObserverEntry final : public ScriptWrappable {
  public:
   IntersectionObserverEntry(DOMHighResTimeStamp timestamp,
                             double intersection_ratio,
-                            const IntRect& bounding_client_rect,
-                            const IntRect* root_bounds,
-                            const IntRect& intersection_rect,
+                            const FloatRect& bounding_client_rect,
+                            const FloatRect* root_bounds,
+                            const FloatRect& intersection_rect,
                             bool is_intersecting,
                             Element*);