Remove logic to reset input method more than needed

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

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 265 matching lines @@
     // |Editor| class.
     if (closeTyping)
         TypingCommand::closeTyping(m_frame);
 
     if (shouldClearTypingStyle)
         clearTypingStyle();
 
     if (m_selectionEditor->visibleSelection<Strategy>() == s) {
         // Even if selection was not changed, selection offsets may have been
         // changed.
-        m_frame->inputMethodController().cancelCompositionIfSelectionIsInvalid();

[yosin_UTC9, 2016/09/28 03:38:50]

Note: This catches replacing Text node with same length of data, e.g. "abc" =>
"ABC", "abc" => "aBc".
But, this can't catch "<b>abc</b>def" => <b>abc</b>XYZdef"; inserting Text node
"XYZ" between "<b>abc</b>" and "def".
In other words, current approach of detecting contents of selection change isn't
enough.

[Changwan Ryu, 2016/09/28 06:20:12]

Hmm.. My understanding is that there is no JS way to change the composition
content. Isn't it the case? (Even if it's not, this CL is still orthogonal to
the composition content handling.)

If the content of the composition cannot change, then there are two possible
ways the composition range can change by JS:
1) part of composition gets removed
2) composition range moves e.g., by inserting text before it.

In most cases the above composition change should accompany selection change. I
could not find a single case where it doesn't.
When selection changes, it will trigger UpdateTextInputState() and
m_compositionRange should have the updated anchor nodes and offsets because
the composition Range is registered to the owner document.

If the above is correct, we can rely on UpdateTextInputState() logic to notify
the composition range update to the browser process.

What do you think?

         notifyLayoutObjectOfSelectionChange(userTriggered);
         return;
     }
 
     const VisibleSelectionTemplate<Strategy> oldSelection = visibleSelection<Strategy>();
     const VisibleSelection oldSelectionInDOMTree = selection();
 
     m_selectionEditor->setVisibleSelection(s, options);
     m_frameCaret->setCaretRectNeedsUpdate();
 
@@ skipping 26 matching lines @@
         // editing/selection/longpress-selection-in-iframe-removed-crash.html
         // reach here.
         return;
     }
     notifyLayoutObjectOfSelectionChange(userTriggered);
     // If the selections are same in the DOM tree but not in the flat tree,
     // don't fire events. For example, if the selection crosses shadow tree
     // boundary, selection for the DOM tree is shrunk while that for the
     // flat tree is not. Additionally, this case occurs in some edge cases.
     // See also: editing/pasteboard/4076267-3.html
-    if (oldSelection == m_selectionEditor->visibleSelection<Strategy>()) {
-        m_frame->inputMethodController().cancelCompositionIfSelectionIsInvalid();

[yosin_UTC9, 2016/09/28 03:38:50]

Ditto as L286.

[Changwan Ryu, 2016/09/28 06:20:12]

Explained in L286.

+    if (oldSelection == m_selectionEditor->visibleSelection<Strategy>())
         return;
-    }
+
     m_frame->editor().respondToChangedSelection(oldSelectionInDOMTree, options);
     if (userTriggered == UserTriggered) {
         ScrollAlignment alignment;
 
         if (m_frame->editor().behavior().shouldCenterAlignWhenSelectionIsRevealed())
             alignment = (align == CursorAlignOnScroll::Always) ? ScrollAlignment::alignCenterAlways : ScrollAlignment::alignCenterIfNeeded;
         else
             alignment = (align == CursorAlignOnScroll::Always) ? ScrollAlignment::alignTopAlways : ScrollAlignment::alignToEdgeIfNeeded;
 
         // TODO(xiaochengh): The use of updateStyleAndLayoutIgnorePendingStylesheets
@@ skipping 1045 matching lines @@
 
 void showTree(const blink::FrameSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
     else
         LOG(INFO) << "Cannot showTree for <null> FrameSelection.";
 }
 
 #endif