12-bit vp9 video support

cc/resources/video_resource_updater_unittest.cc

Index: cc/resources/video_resource_updater_unittest.cc
diff --git a/cc/resources/video_resource_updater_unittest.cc b/cc/resources/video_resource_updater_unittest.cc
index 938c0fc546bdcaef7301b99a822963244e29274a..1c414fc548dc2a4a88efcbbdf4bd508b36df38e4 100644
--- a/cc/resources/video_resource_updater_unittest.cc
+++ b/cc/resources/video_resource_updater_unittest.cc
@@ -504,5 +504,54 @@ TEST_F(VideoResourceUpdaterTest, CreateForHardwarePlanes_StreamTexture) {
   EXPECT_FALSE(context3d_->WasImmutableTextureCreated());
 }
 
+namespace {
+
+// Convert an IEEE 754 half-float to a double value
+// that we can do math on.
+double FromHalfFloat(uint16_t half_float) {
+  if (!half_float)
+    return 0.0;
+  int sign = (half_float & 0x8000) ? -1 : 1;
+  int exponent = (half_float >> 10) & 0x1F;
+  int fraction = half_float & 0x3FF;
+  if (exponent == 0) {
+    return pow(2.0, -24.0) * fraction;
+  } else if (exponent == 0x1F) {
+    return sign * 1000000000000.0;
+  } else {
+    return pow(2.0, exponent - 25) * (0x400 + fraction);
+  }
+}
+
+}  // namespace
+
+TEST_F(VideoResourceUpdaterTest, MakeHalfFloatTest) {
+  unsigned short integers[1 << 12];
+  unsigned short half_floats[1 << 12];
+  for (int bits = 9; bits <= 12; bits++) {
+    int num_values = 1 << bits;
+    for (int i = 0; i < num_values; i++)
+      integers[i] = i;
+
+    VideoResourceUpdater::MakeHalfFloats(integers, bits, num_values,
+                                         half_floats);
+
+    // Multiplier to converting integers to 0.0..1.0 range.
+    double multiplier = 1.0 / (num_values - 1);
+
+    for (int i = 0; i < num_values; i++) {
+      // We expect the result to be within +/- one least-significant bit.
+      // Within the range we care about, half-floats values and
+      // their representation both sort in the same order, so we
+      // can just add one to get the next bigger half-float.
+      float expected_precision =
+          FromHalfFloat(half_floats[i] + 1) - FromHalfFloat(half_floats[i]);
+      EXPECT_NEAR(FromHalfFloat(half_floats[i]), integers[i] * multiplier,
+                  expected_precision)
+          << "i = " << i << " bits = " << bits;
+    }
+  }
+}
+
 }  // namespace
 }  // namespace cc