Unify TouchAction classes

cc/input/touch_action.h

Index: cc/input/touch_action.h
diff --git a/cc/input/touch_action.h b/cc/input/touch_action.h
new file mode 100644
index 0000000000000000000000000000000000000000..1dcdd9a1a119170633f985cb6eee64088328a8ce
--- /dev/null
+++ b/cc/input/touch_action.h
@@ -0,0 +1,45 @@
+// Copyright 2017 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 CC_INPUT_TOUCH_ACTION_H_
+#define CC_INPUT_TOUCH_ACTION_H_
+
+namespace cc {
+
+// The current touch action specifies what accelerated browser operations

[wkorman, 2017/05/08 19:03:01]

Could enhance comments here to add:

- this is intended to be the single canonical definition of the enum
- it's used elsewhere in both Blink and content since touch action logic spans
those subsystems

+// (panning and zooming) are currently permitted via touch input.
+// See http://www.w3.org/TR/pointerevents/#the-touch-action-css-property.
+const size_t kTouchActionBits = 6;

[danakj, 2017/05/09 14:29:46]

whitespace before enum defn

+enum TouchAction {

[jbroman, 2017/05/09 14:40:26]

nit: You might consider enum class, so that you get names like:

TouchAction::kNone

rather than

TouchAction::kTouchActionNone

This may have some consequences (due to the stronger typing it adds), but the
overloaded operator| and operator& might mean that it's not a big deal.

+  // No scrolling or zooming allowed.
+  kTouchActionNone = 0x0,
+  kTouchActionPanLeft = 0x1,
+  kTouchActionPanRight = 0x2,
+  kTouchActionPanX = kTouchActionPanLeft | kTouchActionPanRight,
+  kTouchActionPanUp = 0x4,
+  kTouchActionPanDown = 0x8,
+  kTouchActionPanY = kTouchActionPanUp | kTouchActionPanDown,
+  kTouchActionPan = kTouchActionPanX | kTouchActionPanY,
+  kTouchActionPinchZoom = 0x10,
+  kTouchActionManipulation = kTouchActionPan | kTouchActionPinchZoom,
+  kTouchActionDoubleTapZoom = 0x20,
+  kTouchActionAuto = kTouchActionManipulation | kTouchActionDoubleTapZoom,
+  kTouchActionMax = (1 << 6) - 1
+};
+inline TouchAction operator|(TouchAction a, TouchAction b) {

[danakj, 2017/05/09 14:29:46]

whitespace before/after functions

+  return static_cast<TouchAction>(int(a) | int(b));
+}
+inline TouchAction& operator|=(TouchAction& a, TouchAction b) {
+  return a = a | b;
+}
+inline TouchAction operator&(TouchAction a, TouchAction b) {
+  return static_cast<TouchAction>(int(a) & int(b));
+}
+inline TouchAction& operator&=(TouchAction& a, TouchAction b) {
+  return a = a & b;
+}
+
+}  // namespace cc
+
+#endif  // CC_INPUT_TOUCH_ACTION_H_