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

Source/core/page/EventHandler.cpp

Index: Source/core/page/EventHandler.cpp
diff --git a/Source/core/page/EventHandler.cpp b/Source/core/page/EventHandler.cpp
index 581c19aaae92a86def83dc537eece758ee1afc01..59e100af26780feff0049de13bdb410f93450ca6 100644
--- a/Source/core/page/EventHandler.cpp
+++ b/Source/core/page/EventHandler.cpp
@@ -579,7 +579,7 @@ bool EventHandler::handleMousePressEventSingleClick(const MouseEventWithHitTestR
             granularity = m_frame->selection().granularity();
             newSelection.expandUsingGranularity(m_frame->selection().granularity());
         }
-    } else {
+    } else if (m_selectionInitiationState != ExtendedSelection) {
         newSelection = expandSelectionToRespectUserSelectAll(innerNode, VisibleSelection(visiblePos));
     }
 
@@ -647,7 +647,6 @@ bool EventHandler::handleMousePressEvent(const MouseEventWithHitTestResults& eve
 
     bool swallowEvent = false;
     m_mousePressed = true;
-    m_selectionInitiationState = HaveNotStartedSelection;
 
     if (event.event().clickCount() == 2)
         swallowEvent = handleMousePressEventDoubleClick(event);
@@ -1332,6 +1331,10 @@ bool EventHandler::handleMousePressEvent(const PlatformMouseEvent& mouseEvent)
     m_frame->selection().setCaretBlinkingSuspended(true);
 
     bool swallowEvent = !dispatchMouseEvent(EventTypeNames::mousedown, mev.innerNode(), m_clickCount, mouseEvent, true);
+    // m_selectionInitiationState is initialized after dispatching mousedown event in order not to keep the selection by DOM APIs
+    // Because we can't give the user the chance to handle the selection by user action like dragging if we keep the selection in case of mousedown.
+    // FireFox also has the same behavior and it's more compatible with other browsers.
+    m_selectionInitiationState = HaveNotStartedSelection;
     HitTestResult hitTestResult = hitTestResultInFrame(m_frame, mouseEvent.position(), HitTestRequest::ReadOnly);
     swallowEvent = swallowEvent || handleMouseFocus(MouseEventWithHitTestResults(mouseEvent, hitTestResult));
     m_capturesDragging = !swallowEvent || mev.scrollbar();
@@ -2352,6 +2355,7 @@ bool EventHandler::handleGestureTap(const GestureEventWithHitTestResults& target
         static_cast<PlatformEvent::Modifiers>(modifiers | PlatformEvent::LeftButtonDown),
         PlatformMouseEvent::FromTouch,  gestureEvent.timestamp());
     bool swallowMouseDownEvent = !dispatchMouseEvent(EventTypeNames::mousedown, currentHitTest.innerNode(), gestureEvent.tapCount(), fakeMouseDown, true);
+    m_selectionInitiationState = HaveNotStartedSelection;
     if (!swallowMouseDownEvent)
         swallowMouseDownEvent = handleMouseFocus(MouseEventWithHitTestResults(fakeMouseDown, currentHitTest));
     if (!swallowMouseDownEvent)
@@ -3126,6 +3130,16 @@ void EventHandler::notifyElementActivated()
     m_lastDeferredTapElement = nullptr;
 }
 
+void EventHandler::notifySelectionChanged()

[yosin_UTC9, 2015/04/10 02:06:09]

It is better to move selection handling code in EventHandler to FrameSeleciton,
or new class SelectionController. I feel strange that FrameSelection needs to
notify about selection change to EventHandler.

[Miyoung Shin(g), 2015/04/22 15:32:37]

I've tried to move the code related to the selection from EventHandler to
SelectionHandler.
I'm looking forward to getting your feedback.

[yosin_UTC9, 2015/04/28 01:59:54]

Yes, I'm thinking to have a SelectionHandler class. Although, we need to use
better name other than SelectionHandler, or SelectionController.

+{
+    if (m_frame->selection().isRange())
+        m_selectionInitiationState = ExtendedSelection;

[yosin_UTC9, 2015/04/10 02:06:09]

|m_selectionInitiationState| is no longer represent initiation state. It seems
it represent current state of selection, but enum fields aren't reflected it.

[Miyoung Shin(g), 2015/04/22 15:32:37]

I've changed |m_selectionInitiationState| to |m_selectionState| to be explicit.
Could you explain "enum fields aren't reflected it" that you mentioned in more
detail ?

[yosin_UTC9, 2015/04/28 01:59:54]

I mean |PlacedCaret| and |ExtendSelection| are state after modification rather
than initial state. If we name to |m_selectionState|, I'm OK.

+    else if (m_frame->selection().isCaret())
+        m_selectionInitiationState = PlacedCaret;
+    else
+        m_selectionInitiationState = HaveNotStartedSelection;
+}
+
 bool EventHandler::handleAccessKey(const PlatformKeyboardEvent& evt)
 {
     // FIXME: Ignoring the state of Shift key is what neither IE nor Firefox do.