Write mojom and StructTraits for display::GammaRampRGBEntry

ui/display/mojo/gamma_ramp_rgb_entry.mojom

Index: ui/display/mojo/gamma_ramp_rgb_entry.mojom
diff --git a/ui/display/mojo/gamma_ramp_rgb_entry.mojom b/ui/display/mojo/gamma_ramp_rgb_entry.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..db2d7ed3a7f2e0753abf956116f3d17793a2cf8c
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+++ b/ui/display/mojo/gamma_ramp_rgb_entry.mojom
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+// 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.
+
+module display.mojom;
+
+// Corresponds to display::GammaRampRGBEntry.
+struct GammaRampRGBEntry {
+  uint16 r;
+  uint16 g;
+  uint16 b;
+};