Revert of Move logic of recording main thread scrolling reasons from cc to blink::ScrollManager

third_party/WebKit/Source/core/input/ScrollManager.cpp

Index: third_party/WebKit/Source/core/input/ScrollManager.cpp
diff --git a/third_party/WebKit/Source/core/input/ScrollManager.cpp b/third_party/WebKit/Source/core/input/ScrollManager.cpp
index 76a67a5702c3dd154cfc2454c718d515740b14a8..cd8ace43239b75d60b2304179281472207e2a849 100644
--- a/third_party/WebKit/Source/core/input/ScrollManager.cpp
+++ b/third_party/WebKit/Source/core/input/ScrollManager.cpp
@@ -22,7 +22,6 @@
 #include "core/page/scrolling/RootScrollerController.h"
 #include "core/page/scrolling/ScrollState.h"
 #include "core/paint/PaintLayer.h"
-#include "platform/Histogram.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "wtf/PtrUtil.h"
 
@@ -197,67 +196,6 @@
   scroll_state.distributeToScrollChainDescendant();
 }
 
-uint32_t ScrollManager::ComputeNonCompositedMainThreadScrollingReasons() {
-  // When scrolling on the main thread, the scrollableArea may or may not be
-  // composited. Either way, we have recorded either the reasons stored in
-  // its layer or the reason NonFastScrollableRegion from the compositor
-  // side. Here we record scrolls that occurred on main thread due to a
-  // non-composited scroller.
-  if (!scroll_gesture_handling_node_->GetLayoutObject() || !frame_->View())
-    return 0;
-
-  uint32_t non_composited_main_thread_scrolling_reasons = 0;
-
-  for (auto* cur_box =
-           scroll_gesture_handling_node_->GetLayoutObject()->EnclosingBox();
-       cur_box; cur_box = cur_box->ContainingBlock()) {
-    PaintLayerScrollableArea* scrollable_area = cur_box->GetScrollableArea();
-
-    if (!scrollable_area || !scrollable_area->ScrollsOverflow())
-      continue;
-
-    DCHECK(!scrollable_area->UsesCompositedScrolling() ||
-           !scrollable_area->GetNonCompositedMainThreadScrollingReasons());
-    non_composited_main_thread_scrolling_reasons |=
-        scrollable_area->GetNonCompositedMainThreadScrollingReasons();
-  }
-
-  return non_composited_main_thread_scrolling_reasons;
-}
-
-void ScrollManager::RecordNonCompositedMainThreadScrollingReasons(
-    const WebGestureDevice device) {
-  if (device != kWebGestureDeviceTouchpad &&
-      device != kWebGestureDeviceTouchscreen) {
-    return;
-  }
-
-  uint32_t reasons = ComputeNonCompositedMainThreadScrollingReasons();
-  if (!reasons)
-    return;
-  DCHECK(MainThreadScrollingReason::HasNonCompositedScrollReasons(reasons));
-
-  uint32_t main_thread_scrolling_reason_enum_max =
-      MainThreadScrollingReason::kMainThreadScrollingReasonCount + 1;
-  for (uint32_t i = MainThreadScrollingReason::kNonCompositedReasonsFirst;
-       i <= MainThreadScrollingReason::kNonCompositedReasonsLast; ++i) {
-    unsigned val = 1 << i;
-    if (reasons & val) {
-      if (device == kWebGestureDeviceTouchscreen) {
-        DEFINE_STATIC_LOCAL(EnumerationHistogram, touch_histogram,
-                            ("Renderer4.MainThreadGestureScrollReason",
-                             main_thread_scrolling_reason_enum_max));
-        touch_histogram.Count(i + 1);
-      } else {
-        DEFINE_STATIC_LOCAL(EnumerationHistogram, wheel_histogram,
-                            ("Renderer4.MainThreadWheelScrollReason",
-                             main_thread_scrolling_reason_enum_max));
-        wheel_histogram.Count(i + 1);
-      }
-    }
-  }
-}
-
 WebInputEventResult ScrollManager::HandleGestureScrollBegin(
     const WebGestureEvent& gesture_event) {
   Document* document = frame_->GetDocument();
@@ -282,8 +220,6 @@
 
   PassScrollGestureEvent(gesture_event,
                          scroll_gesture_handling_node_->GetLayoutObject());
-
-  RecordNonCompositedMainThreadScrollingReasons(gesture_event.source_device);
 
   current_scroll_chain_.clear();
   std::unique_ptr<ScrollStateData> scroll_state_data =