cc: Fix enum style conformance in InputHandler.

cc/input/main_thread_scrolling_reason.h

+// Copyright 2016 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_MAIN_THREAD_SCROLLING_REASON_H_
+#define CC_INPUT_MAIN_THREAD_SCROLLING_REASON_H_
+
+namespace cc {
+
+// Ensure this stays in sync with MainThreadScrollingReason in histograms.xml,
+// and that this extends ScrollingCoordinator::MainThreadScrollingReason.
+// ScrollingCoordinator::MainThreadScrollingReason contains the flags
+// which are associated with a layer. The flags only contained in
+// MainThreadScrollingReason are computed for each scroll begin.
+struct MainThreadScrollingReason {
+  // Non-transient scrolling reasons.
+  enum : uint32_t { kNotScrollingOnMain = 0 };
+  enum : uint32_t { kHasBackgroundAttachmentFixedObjects = 1 << 0 };
+  // TODO(tdresser): Unused. Remove?
+  enum : uint32_t { kHasNonLayerViewportConstrainedObjects = 1 << 1 };
+  // TODO(tdresser): Unused. Remove?
+  enum : uint32_t { kThreadedScrollingDisabled = 1 << 2 };
+  enum : uint32_t { kScrollbarScrolling = 1 << 3 };
+  // TODO(tdresser): Unused. Remove?
+  enum : uint32_t { kPageOverlay = 1 << 4 };
+  enum : uint32_t { kMaxNonTransientScrollingReason = kPageOverlay };

[tdresser, 2016/01/20 15:17:27]

These will be used after your other change.

See
https://codereview.chromium.org/1602773006/diff/60001/third_party/WebKit/Sour...
for example.

Some of these constants were only used on the blink side, but once the enums are
merged, everything should be used.

[danakj, 2016/01/20 21:00:01]

Done.

+
+  // Transcient scrolling reasons.

[tdresser, 2016/01/20 15:17:27]

Can you fix my spelling here too?
"Transient"

Thanks!

[danakj, 2016/01/20 21:00:01]

Done.

+  enum : uint32_t { kNonFastScrollableRegion = 1 << 5 };
+  enum : uint32_t { kEventHandlers = 1 << 6 };
+  enum : uint32_t { kFailedHitTest = 1 << 7 };
+  enum : uint32_t { kNoScrollingLayer = 1 << 8 };
+  enum : uint32_t { kNotScrollable = 1 << 9 };
+  enum : uint32_t { kContinuingMainThreadScroll = 1 << 10 };
+  enum : uint32_t { kNonInvertibleTransform = 1 << 11 };
+
+  // The number of flags in this struct (excluding itself).
+  enum : uint32_t { kMainThreadScrollingReasonCount = 13 };
+};
+
+}  // namespace cc
+
+#endif  // CC_INPUT_MAIN_THREAD_SCROLLING_REASON_H_