Do not send redundant selectionchange-events (decouple focus)

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

Index: third_party/WebKit/Source/core/editing/EditingUtilities.cpp
diff --git a/third_party/WebKit/Source/core/editing/EditingUtilities.cpp b/third_party/WebKit/Source/core/editing/EditingUtilities.cpp
index 334c6e74659019cc3cbbd7852cc4ecd23cadc981..844e7060a4e17e95e3b029a875e22194cc653e52 100644
--- a/third_party/WebKit/Source/core/editing/EditingUtilities.cpp
+++ b/third_party/WebKit/Source/core/editing/EditingUtilities.cpp
@@ -372,6 +372,43 @@ Element* rootEditableElement(const Node& node) {
   return toElement(const_cast<Node*>(result));
 }
 
+bool isSelectionInDocument(const VisibleSelectionInFlatTree& visibleSelection,
+                           const Document& document) {
+  const PositionInFlatTree& start = visibleSelection.start();
+  if (start.isNotNull() &&
+      (!start.isConnected() || start.document() != document))
+    return false;
+  const PositionInFlatTree& end = visibleSelection.end();
+  if (end.isNotNull() && (!end.isConnected() || end.document() != document))
+    return false;
+  const PositionInFlatTree extent = visibleSelection.extent();
+  if (extent.isNotNull() &&
+      (!extent.isConnected() || extent.document() != document))
+    return false;
+  return true;
+}
+
+bool selectionHasFocus(const LocalFrame& frame) {
+  const VisibleSelectionInFlatTree& selection =
+      frame.selection().computeVisibleSelectionInFlatTree();
+  if (!isSelectionInDocument(selection, *frame.document()))

[yosin_UTC9, 2017/03/21 06:49:59]

We can assume SelectionInFlatTree in FrameSeleciton always isNone() or
isConnected().
So, we don't need to use isSelectionInDocument().

[hugoh_UTC2, 2017/03/22 02:54:47]

Done.

+    return false;
+
+  const Element* focus = frame.document()->focusedElement();
+  if (!focus) {
+    // No focused element means document root has focus.
+    focus = frame.document()->documentElement();
+  }
+
+  const Node* const nodeWhereSelectionStarts =

[yosin_UTC9, 2017/03/21 06:49:59]

To check base/extent in focus element, we don't need to use
|VisibleSelectionInFlatTree|, please use |SelectionInFlatTree| here.

[hugoh_UTC2, 2017/03/22 02:54:47]

FrameSelection has no public getter that returns the |SelectionInFlatTree|...
Isn't computeVisibleSelectionInFlatTree() quick to call since it uses caching?

+      selection.base().computeContainerNode();
+  const Node* const nodeWhereSelectionEnds =
+      selection.extent().computeContainerNode();
+
+  return focus->containsIncludingHostElements(*nodeWhereSelectionStarts) ||
+         focus->containsIncludingHostElements(*nodeWhereSelectionEnds);
+}
+
 ContainerNode* highestEditableRoot(
     const Position& position,
     Element* (*rootEditableElementOf)(const Position&),