First-cut at fixing unhandled Tap event returns in Blink.

Source/core/page/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * 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.
@@ skipping 212 matching lines @@
     , m_widgetIsLatched(false)
     , m_touchPressed(false)
     , m_scrollGestureHandlingNode(nullptr)
     , m_lastHitTestResultOverWidget(false)
     , m_maxMouseMovedDuration(0)
     , m_baseEventType(PlatformEvent::NoType)
     , m_didStartDrag(false)
     , m_longTapShouldInvokeContextMenu(false)
     , m_activeIntervalTimer(this, &EventHandler::activeIntervalTimerFired)
     , m_lastShowPressTimestamp(0)
+    , m_fixTapGestureReturnValue(false)
 {
 }
 
 EventHandler::~EventHandler()
 {
     ASSERT(!m_fakeMouseMoveEventTimer.isActive());
 }
 
 DragState& EventHandler::dragState()
 {
@@ skipping 364 matching lines @@
     bool swallowEvent = false;
     m_mousePressed = true;
     m_selectionInitiationState = HaveNotStartedSelection;
 
     if (event.event().clickCount() == 2)
         swallowEvent = handleMousePressEventDoubleClick(event);
     else if (event.event().clickCount() >= 3)
         swallowEvent = handleMousePressEventTripleClick(event);
     else
         swallowEvent = handleMousePressEventSingleClick(event);
+    if (m_fixTapGestureReturnValue)
+        swallowEvent = false;

[Rick Byers, 2014/05/16 11:10:43]

This seems wrong.  A click from touch is as legitimate as a click from mouse
(it's not "fake" - click really means activate and is sent for keyboard as
well).  So, for example, if a webpage calls preventDefault on click then you
should absolutely NOT be doing some extra browser UI in that case ("content not
chrome" - the app owns it's event stream first).

[Donn Denman, 2014/05/27 05:58:14]

Done.

 
     m_mouseDownMayStartAutoscroll = m_mouseDownMayStartSelect
         || (m_mousePressNode && m_mousePressNode->renderBox() && m_mousePressNode->renderBox()->canBeProgramaticallyScrolled());
 
     return swallowEvent;
 }
 
 bool EventHandler::handleMouseDraggedEvent(const MouseEventWithHitTestResults& event)
 {
     TRACE_EVENT0("webkit", "EventHandler::handleMouseDraggedEvent");
@@ skipping 1595 matching lines @@
     if (gestureEvent.shiftKey())
         modifierFlags |= PlatformEvent::ShiftKey;
     PlatformEvent::Modifiers modifiers = static_cast<PlatformEvent::Modifiers>(modifierFlags);
 
     PlatformMouseEvent fakeMouseMove(adjustedPoint, gestureEvent.globalPosition(),
         NoButton, PlatformEvent::MouseMoved, /* clickCount */ 0,
         modifiers, PlatformMouseEvent::FromTouch, gestureEvent.timestamp());
     handleMouseMoveEvent(fakeMouseMove);
 
     bool defaultPrevented = false;
+    m_fixTapGestureReturnValue = true;
     PlatformMouseEvent fakeMouseDown(adjustedPoint, gestureEvent.globalPosition(),
         LeftButton, PlatformEvent::MousePressed, gestureEvent.tapCount(),
         modifiers, PlatformMouseEvent::FromTouch,  gestureEvent.timestamp());
     defaultPrevented |= handleMousePressEvent(fakeMouseDown);
 
     PlatformMouseEvent fakeMouseUp(adjustedPoint, gestureEvent.globalPosition(),
         LeftButton, PlatformEvent::MouseReleased, gestureEvent.tapCount(),
         modifiers, PlatformMouseEvent::FromTouch,  gestureEvent.timestamp());
     defaultPrevented |= handleMouseReleaseEvent(fakeMouseUp);
+    // TODO(donnd): do we need to worry about exceptions being thrown above?
+    m_fixTapGestureReturnValue = false;
 
     return defaultPrevented;
 }
 
 bool EventHandler::handleGestureLongPress(const PlatformGestureEvent& gestureEvent, const IntPoint& adjustedPoint)
 {
     m_longTapShouldInvokeContextMenu = false;
     if (m_frame->settings() && m_frame->settings()->touchDragDropEnabled() && m_frame->view()) {
         PlatformMouseEvent mouseDownEvent(adjustedPoint, gestureEvent.globalPosition(), LeftButton, PlatformEvent::MousePressed, 1,
             gestureEvent.shiftKey(), gestureEvent.ctrlKey(), gestureEvent.altKey(), gestureEvent.metaKey(), WTF::currentTime());
@@ skipping 1482 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace WebCore