"Find" scrolling should be smoothly animated.

third_party/WebKit/Source/core/editing/Editor.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 1597 matching lines @@
 
 Range* Editor::FindStringAndScrollToVisible(const String& target,
                                             Range* previous_match,
                                             FindOptions options) {
   Range* next_match = FindRangeOfString(
       target, EphemeralRangeInFlatTree(previous_match), options);
   if (!next_match)
     return nullptr;
 
   Node* first_node = next_match->FirstNode();
-  first_node->GetLayoutObject()->ScrollRectToVisible(
-      LayoutRect(next_match->BoundingBox()),
-      ScrollAlignment::kAlignCenterIfNeeded,
-      ScrollAlignment::kAlignCenterIfNeeded, kUserScroll);

[sunyunjia, 2017/06/12 21:17:57]

Not sure why this was kUserScroll. Perhaps we should also change it to
kProgrammaticScroll?

[bokan, 2017/06/13 01:48:08]

Acknowledged.

+  first_node->GetDocument()

[bokan, 2017/06/13 01:48:08]

This leaks too many details of how smooth scroll are implemented. Lets rearrange
LayoutBox::ScrollRectToVisible a little; move the current implementation into
ScrollRectToVisibleRecursive and call it from ScrollRectToVisible.
LayoutBox::ScrollRectToVisible should call Abort and RunQueuedAnimations if the
scroll is smooth. 

[sunyunjia, 2017/06/13 17:45:11]

Done.

+      .GetPage()
+      ->GetSmoothScrollSequencer()
+      ->AbortAnimations();
+  if (RuntimeEnabledFeatures::CSSOMSmoothScrollEnabled()) {

[bokan, 2017/06/13 01:48:08]

This has no web-facing consequences so there's no need to guard it behind the
flag. Lets just make this smooth in all cases.

[sunyunjia, 2017/06/13 17:45:11]

Done.

+    first_node->GetLayoutObject()->ScrollRectToVisible(
+        LayoutRect(next_match->BoundingBox()),
+        ScrollAlignment::kAlignCenterIfNeeded,
+        ScrollAlignment::kAlignCenterIfNeeded, kProgrammaticScroll, true,
+        kScrollBehaviorSmooth);
+    first_node->GetDocument()
+        .GetPage()
+        ->GetSmoothScrollSequencer()
+        ->RunQueuedAnimations();
+  } else {
+    first_node->GetLayoutObject()->ScrollRectToVisible(
+        LayoutRect(next_match->BoundingBox()),
+        ScrollAlignment::kAlignCenterIfNeeded,
+        ScrollAlignment::kAlignCenterIfNeeded, kUserScroll);
+  }
   first_node->GetDocument().SetSequentialFocusNavigationStartingPoint(
       first_node);
 
   return next_match;
 }
 
 // TODO(yosin) We should return |EphemeralRange| rather than |Range|. We use
 // |Range| object for checking whether start and end position crossing shadow
 // boundaries, however we can do it without |Range| object.
 template <typename Strategy>
@@ skipping 209 matching lines @@
 
 DEFINE_TRACE(Editor) {
   visitor->Trace(frame_);
   visitor->Trace(last_edit_command_);
   visitor->Trace(undo_stack_);
   visitor->Trace(mark_);
   visitor->Trace(typing_style_);
 }
 
 }  // namespace blink