Remove logic to reset input method more than needed

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 61653f2e4bb10791e9c466b62f9ad4886b742cbb..bad3d9ed3ca9cc2621759ccd934657edf3e20352 100644
--- a/third_party/WebKit/Source/core/editing/FrameSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
@@ -283,7 +283,6 @@ void FrameSelection::setSelectionAlgorithm(const VisibleSelectionTemplate<Strate
     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;
     }
@@ -330,10 +329,9 @@ void FrameSelection::setSelectionAlgorithm(const VisibleSelectionTemplate<Strate
     // 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;