Move touch CTM from X into Chrome

ui/events/touch_transformer.h

+// Copyright (c) 2014 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.
+
+#ifndef UI_EVENTS_TOUCH_TRANSFORMER_H_
+#define UI_EVENTS_TOUCH_TRANSFORMER_H_
+
+#include "ui/events/events_base_export.h"
+
+namespace ui {
+
+// TouchTransformer is used to map touch events coordinate from screen space
+// to root window space.
+// When touch events are reported from kernel, its coordinate is in device
+// space. After passing through X, its coordinate gets mapped to screen
+// space, e.g. the framebuffer space that is the combination of multiple
+// display outputs.
+// In Chrome, we use TouchTransformer to remap the touch event's location from
+// the screen space to the root window space.
+struct EVENTS_BASE_EXPORT TouchTransformer {
+ public:
+  TouchTransformer();
+
+  float x_scale;
+  float x_offset;
+  float y_scale;
+  float y_offset;
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_TOUCH_TRANSFORMER_H_