Delay instantiating InputDeviceCapabilities until accessed.

third_party/WebKit/Source/core/input/InputDeviceCapabilities.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/input/InputDeviceCapabilities.h"
 
+#include "core/frame/DOMWindow.h"
+
 namespace blink {
 
-InputDeviceCapabilities::InputDeviceCapabilities(bool firesTouchEvents) {
-  m_firesTouchEvents = firesTouchEvents;
-}
-
 InputDeviceCapabilities::InputDeviceCapabilities(
     const InputDeviceCapabilitiesInit& initializer) {
   m_firesTouchEvents = initializer.firesTouchEvents();
 }
 
-InputDeviceCapabilities* InputDeviceCapabilitiesConstants::firesTouchEvents(
-    bool firesTouch) {
-  if (firesTouch) {
-    if (!m_firesTouchEvents)
-      m_firesTouchEvents = InputDeviceCapabilities::create(true);
-    return m_firesTouchEvents;
-  }
-  if (!m_doesntFireTouchEvents)
-    m_doesntFireTouchEvents = InputDeviceCapabilities::create(false);
-  return m_doesntFireTouchEvents;
+InputDeviceCapabilities::InputDeviceCapabilities(
+    InputDeviceCapabilities::Descriptor descriptor)
+    : m_firesTouchEvents(descriptor & FiresTouchEvents) {}
+
+InputDeviceCapabilities* InputDeviceCapabilitiesValue::getCapabilities(
+    DOMWindow* window) {
+  if (m_capabilities)
+    return m_capabilities;
+
+  if (m_descriptor == InputDeviceCapabilities::Null)
+    return nullptr;
+
+  if (window)
+    m_capabilities = window->getInputDeviceCapabilities()->get(m_descriptor);
+  else
+    m_capabilities = InputDeviceCapabilities::create(m_descriptor);
+
+  return m_capabilities;
+}
+
+InputDeviceCapabilities* InputDeviceCapabilitiesConstants::get(
+    InputDeviceCapabilities::Descriptor descriptor) {
+  if (descriptor == InputDeviceCapabilities::Null)
+    return nullptr;
+  Member<InputDeviceCapabilities>& result = m_doesntFireTouchEvents;
+  if (descriptor & InputDeviceCapabilities::FiresTouchEvents)
+    result = m_firesTouchEvents;
+  if (!result)
+    result = InputDeviceCapabilities::create(descriptor);
+  return result;
 }
 
 }  // namespace blink