Create FP16 LUTs when needed

ui/gfx/half_float.cc

Index: ui/gfx/half_float.cc
diff --git a/ui/gfx/half_float.cc b/ui/gfx/half_float.cc
new file mode 100644
index 0000000000000000000000000000000000000000..930d0cacce954a1882468ab18e129e2764d35186
--- /dev/null
+++ b/ui/gfx/half_float.cc
@@ -0,0 +1,16 @@
+// Copyright (c) 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.
+
+#include "ui/gfx/half_float.h"
+
+namespace gfx {
+
+void FloatToHalfFloat(const float* input, HalfFloat* output, size_t num) {
+  for (size_t i = 0; i < num; i++) {
+    float tmp = input[i] * 1.9259299444e-34f;
+    uint32_t tmp2 = *reinterpret_cast<uint32_t*>(&tmp) + (1 << 12);
+    output[i] = (tmp2 & 0x80000000UL) >> 16 | (tmp2 >> 13);
+  }
+}
+};