Keep the selection of the text field when changed by JS.

Source/core/editing/SelectionController.cpp

Index: Source/core/editing/SelectionController.cpp
diff --git a/Source/core/editing/SelectionController.cpp b/Source/core/editing/SelectionController.cpp
index 6544f3ce7d923d24655242e3ee59a7adbd8fbac6..d2e0e6678f4664efc926bc0146d4c3362f292dcb 100644
--- a/Source/core/editing/SelectionController.cpp
+++ b/Source/core/editing/SelectionController.cpp
@@ -193,7 +193,7 @@ bool SelectionController::handleMousePressEventSingleClickAlgorithm(const MouseE
             granularity = selection().granularity();
             expandSelectionUsingGranularity(newSelection, selection().granularity());
         }
-    } else {
+    } else if (m_selectionState != SelectionState::ExtendedSelection) {
         newSelection = expandSelectionToRespectUserSelectAll(innerNode, VisibleSelection(visiblePos));
     }
 
@@ -618,6 +618,16 @@ bool SelectionController::mouseDownWasSingleClickInSelection() const
     return m_mouseDownWasSingleClickInSelection;
 }
 
+void SelectionController::notifySelectionChanged()
+{

[yosin_UTC9, 2015/07/06 01:57:30]

It is better to have a function which maps |SelectionType| to |SelectionState|.
Or, use |SelectionType| instead of |SelectionState|.

BTW, what difference between |m_selectionState| and
|m_frame->selection().selection().selectionType()|? Do we need to keep tracking
selection type in both |FrameSelection| and |SelectionController|?

[Miyoung Shin(g), 2015/07/13 03:32:57]

Done.
IIUC, |m_selectionState| works together for events so it can be changed to the
range status as |m_frame->selection().selection().selectionType()| is not the
range yet.
eg. when starting dragging the mouse on text, |m_selectionState| is set to
|SelectionState::ExtendedSelection| first in
|SelectionController::updateSelectionForMouseDragAlgorithm|. At that time,
|selectionType()| is still |SelectionType::CaretSelection|.
And then, when handling the next mouse event we can keep the selection range.

Also, even if |selectionType()| is |SelectionType::RangeSelection| when handling
the mouse release event, we can clear the selection through |m_selectionState|.

+    if (selection().isRange())
+        m_selectionState = SelectionState::ExtendedSelection;
+    else if (selection().isCaret())
+        m_selectionState = SelectionState::PlacedCaret;
+    else
+        m_selectionState = SelectionState::HaveNotStartedSelection;
+}
+
 FrameSelection& SelectionController::selection() const
 {
     return m_frame->selection();