Change External Texture YUV-to-RGB Conversion to Use Matrix

Changes Dawn and Tint to use a 3x3 matrix for external texture
YUV-to-RGB conversions. This will allow us to use standard matrices
as they exist in SkYuvMath.

Bugs: dawn::1082
Change-Id: I8e0c7c3dc1c085d8f336da956aea9496913b70fa
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/86847
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Brandon1 Jones <brandon1.jones@intel.com>
diff --git a/test/tint/builtins/textureLoad/texture_external_param.wgsl.expected.hlsl b/test/tint/builtins/textureLoad/texture_external_param.wgsl.expected.hlsl
index e7f6715..e821392 100644
--- a/test/tint/builtins/textureLoad/texture_external_param.wgsl.expected.hlsl
+++ b/test/tint/builtins/textureLoad/texture_external_param.wgsl.expected.hlsl
@@ -1,43 +1,39 @@
 struct ExternalTextureParams {
   uint numPlanes;
-  float vr;
-  float ug;
-  float vg;
-  float ub;
+  float3x4 yuvToRgbConversionMatrix;
 };
 
 Texture2D<float4> ext_tex_plane_1 : register(t1, space1);
 cbuffer cbuffer_ext_tex_params : register(b2, space1) {
-  uint4 ext_tex_params[2];
+  uint4 ext_tex_params[4];
 };
 Texture2D<float4> arg_0 : register(t0, space1);
 
 float4 textureLoadExternal(Texture2D<float4> plane0, Texture2D<float4> plane1, int2 coord, ExternalTextureParams params) {
+  float3 color = float3(0.0f, 0.0f, 0.0f);
   if ((params.numPlanes == 1u)) {
-    return plane0.Load(int3(coord, 0));
+    color = plane0.Load(int3(coord, 0)).rgb;
+  } else {
+    color = mul(params.yuvToRgbConversionMatrix, float4(plane0.Load(int3(coord, 0)).r, plane1.Load(int3(coord, 0)).rg, 1.0f));
   }
-  const float y = (plane0.Load(int3(coord, 0)).r - 0.0625f);
-  const float2 uv = (plane1.Load(int3(coord, 0)).rg - 0.5f);
-  const float u = uv.x;
-  const float v = uv.y;
-  const float r = ((1.164000034f * y) + (params.vr * v));
-  const float g = (((1.164000034f * y) - (params.ug * u)) - (params.vg * v));
-  const float b = ((1.164000034f * y) + (params.ub * u));
-  return float4(r, g, b, 1.0f);
+  return float4(color, 1.0f);
 }
 
 float4 textureLoad2d(Texture2D<float4> tint_symbol, Texture2D<float4> ext_tex_plane_1_1, ExternalTextureParams ext_tex_params_1, int2 coords) {
   return textureLoadExternal(tint_symbol, ext_tex_plane_1_1, coords, ext_tex_params_1);
 }
 
-ExternalTextureParams tint_symbol_2(uint4 buffer[2], uint offset) {
+float3x4 tint_symbol_4(uint4 buffer[4], uint offset) {
   const uint scalar_offset = ((offset + 0u)) / 4;
-  const uint scalar_offset_1 = ((offset + 4u)) / 4;
-  const uint scalar_offset_2 = ((offset + 8u)) / 4;
-  const uint scalar_offset_3 = ((offset + 12u)) / 4;
-  const uint scalar_offset_4 = ((offset + 16u)) / 4;
-  const ExternalTextureParams tint_symbol_5 = {buffer[scalar_offset / 4][scalar_offset % 4], asfloat(buffer[scalar_offset_1 / 4][scalar_offset_1 % 4]), asfloat(buffer[scalar_offset_2 / 4][scalar_offset_2 % 4]), asfloat(buffer[scalar_offset_3 / 4][scalar_offset_3 % 4]), asfloat(buffer[scalar_offset_4 / 4][scalar_offset_4 % 4])};
-  return tint_symbol_5;
+  const uint scalar_offset_1 = ((offset + 16u)) / 4;
+  const uint scalar_offset_2 = ((offset + 32u)) / 4;
+  return float3x4(asfloat(buffer[scalar_offset / 4]), asfloat(buffer[scalar_offset_1 / 4]), asfloat(buffer[scalar_offset_2 / 4]));
+}
+
+ExternalTextureParams tint_symbol_2(uint4 buffer[4], uint offset) {
+  const uint scalar_offset_3 = ((offset + 0u)) / 4;
+  const ExternalTextureParams tint_symbol_6 = {buffer[scalar_offset_3 / 4][scalar_offset_3 % 4], tint_symbol_4(buffer, (offset + 16u))};
+  return tint_symbol_6;
 }
 
 void doTextureLoad() {