Do not send redundant selectionchange-events (decouple focus)

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

Index: third_party/WebKit/Source/core/editing/FrameSelection.cpp
diff --git a/third_party/WebKit/Source/core/editing/FrameSelection.cpp b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
index 6467d40158b462f9ef3272f1b678b2bd85edc4b7..d85af769ad84b284ac3e0f051cb583d43a133543 100644
--- a/third_party/WebKit/Source/core/editing/FrameSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
@@ -250,7 +250,7 @@ void FrameSelection::DidSetSelectionDeprecated(SetSelectionOptions options,
   }
 
   frame_caret_->StopCaretBlinkTimer();
-  UpdateAppearance();
+  UpdateAppearance(LayoutSelection::PaintHint::kPaint);
 
   // Always clear the x position used for vertical arrow navigation.
   // It will be restored by the vertical arrow navigation code if necessary.
@@ -335,7 +335,21 @@ void FrameSelection::DidChangeFocus() {
   // Hits in
   // virtual/gpu/compositedscrolling/scrollbars/scrollbar-miss-mousemove-disabled.html
   DisableCompositingQueryAsserts disabler;
-  UpdateAppearance();
+
+  const Element* focus = GetDocument().FocusedElement();

[yosin_UTC9, 2017/04/13 09:31:50]

Since Document::FocusedElement() is simple getter.

We can write

const Element* const focus = GetDocument().FocusedElement() ?
GetDocument().FocusedElement() : GetDOcument.documentElement();
if (!focus) {
  // No focused element means document root has focus.
  return;
}

[hugoh_UTC2, 2017/04/14 01:34:47]

Done. (But the comment must go above the ternary operator).

+  if (!focus) {
+    // No focused element means document root has focus.
+    focus = GetDocument().documentElement();
+    if (!focus)
+      return;

[yosin_UTC9, 2017/04/13 09:31:50]

We still need to call
frame_caret_->ScheduleVisualUpdateForPaintInvalidationIfNeeded();

We should rest |text_control_focus_| to false.

[hugoh_UTC2, 2017/04/14 01:34:47]

Done.
Done. We need this early return to protect us from
LayoutTests/editing/selection/selection-crash.html (I've now added a comment
about that), in all other cases I've tried, focus has been an Element (or
documentElement). So I was thinking this exceptional case should rather "keep
current value". But let's reset it to false for consistency if you prefer. 

+  }
+  // Hide the selection when focus goes away from a text-field and into
+  // something that is not a text-field. When focus enters another text-field we
+  // do not need to update appearance; the appearance is updated when the new
+  // selection is set.
+  if (text_control_focus_ && !focus->IsTextControl())
+    UpdateAppearance(LayoutSelection::PaintHint::kHide);
+  text_control_focus_ = focus->IsTextControl();
 }
 
 static DispatchEventResult DispatchSelectStart(
@@ -773,13 +787,15 @@ void FrameSelection::CommitAppearanceIfNeeded(LayoutView& layout_view) {
 }
 
 void FrameSelection::DidLayout() {
-  UpdateAppearance();
+  // Upon relayout, a hidden selection must be kept hidden and a visible
+  // selection must be kept visible.
+  UpdateAppearance(LayoutSelection::PaintHint::kKeep);
 }
 
-void FrameSelection::UpdateAppearance() {
+void FrameSelection::UpdateAppearance(LayoutSelection::PaintHint hint) {
   DCHECK(!frame_->ContentLayoutItem().IsNull());
   frame_caret_->ScheduleVisualUpdateForPaintInvalidationIfNeeded();
-  layout_selection_->SetHasPendingSelection();
+  layout_selection_->SetHasPendingSelection(hint);
 }
 
 void FrameSelection::NotifyLayoutObjectOfSelectionChange(
@@ -970,7 +986,7 @@ void FrameSelection::RevealSelection(const ScrollAlignment& alignment,
       document_loader->GetInitialScrollState().was_scrolled_by_user = true;
     if (start.AnchorNode()->GetLayoutObject()->ScrollRectToVisible(
             rect, alignment, alignment))
-      UpdateAppearance();
+      UpdateAppearance(LayoutSelection::PaintHint::kPaint);
   }
 }