Move tint::transform::Robustness to a santizier transform

There's no good reason for this to be public.
Move it into the writers, and expose a 'disable_robustness' option to
turn it off. This can be expanded to hold more fine-grain control in the
future.

Change-Id: I6ea6e54a27b2ae0fbcba5fdf45539063045cc15a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/122203
Commit-Queue: Ben Clayton <bclayton@google.com>
Kokoro: Ben Clayton <bclayton@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>
diff --git a/test/tint/builtins/gen/literal/textureLoad/1bfdfb.wgsl.expected.glsl b/test/tint/builtins/gen/literal/textureLoad/1bfdfb.wgsl.expected.glsl
index a5f0e0a..598afb2 100644
--- a/test/tint/builtins/gen/literal/textureLoad/1bfdfb.wgsl.expected.glsl
+++ b/test/tint/builtins/gen/literal/textureLoad/1bfdfb.wgsl.expected.glsl
@@ -14,16 +14,22 @@
 struct ExternalTextureParams {
   uint numPlanes;
   uint doYuvToRgbConversionOnly;
+  uint pad;
+  uint pad_1;
   mat3x4 yuvToRgbConversionMatrix;
   GammaTransferParams gammaDecodeParams;
   GammaTransferParams gammaEncodeParams;
   mat3 gamutConversionMatrix;
   mat3x2 coordTransformationMatrix;
+  uint pad_2;
+  uint pad_3;
 };
 
 struct ExternalTextureParams_std140 {
   uint numPlanes;
   uint doYuvToRgbConversionOnly;
+  uint pad;
+  uint pad_1;
   mat3x4 yuvToRgbConversionMatrix;
   GammaTransferParams gammaDecodeParams;
   GammaTransferParams gammaEncodeParams;
@@ -31,6 +37,8 @@
   vec2 coordTransformationMatrix_0;
   vec2 coordTransformationMatrix_1;
   vec2 coordTransformationMatrix_2;
+  uint pad_2;
+  uint pad_3;
 };
 
 layout(binding = 2, std140) uniform ext_tex_params_block_std140_ubo {
@@ -63,7 +71,7 @@
 uniform highp sampler2D arg_0_1;
 uniform highp sampler2D ext_tex_plane_1_1;
 ExternalTextureParams conv_ExternalTextureParams(ExternalTextureParams_std140 val) {
-  return ExternalTextureParams(val.numPlanes, val.doYuvToRgbConversionOnly, val.yuvToRgbConversionMatrix, val.gammaDecodeParams, val.gammaEncodeParams, val.gamutConversionMatrix, mat3x2(val.coordTransformationMatrix_0, val.coordTransformationMatrix_1, val.coordTransformationMatrix_2));
+  return ExternalTextureParams(val.numPlanes, val.doYuvToRgbConversionOnly, val.pad, val.pad_1, val.yuvToRgbConversionMatrix, val.gammaDecodeParams, val.gammaEncodeParams, val.gamutConversionMatrix, mat3x2(val.coordTransformationMatrix_0, val.coordTransformationMatrix_1, val.coordTransformationMatrix_2), val.pad_2, val.pad_3);
 }
 
 void textureLoad_1bfdfb() {
@@ -100,16 +108,22 @@
 struct ExternalTextureParams {
   uint numPlanes;
   uint doYuvToRgbConversionOnly;
+  uint pad;
+  uint pad_1;
   mat3x4 yuvToRgbConversionMatrix;
   GammaTransferParams gammaDecodeParams;
   GammaTransferParams gammaEncodeParams;
   mat3 gamutConversionMatrix;
   mat3x2 coordTransformationMatrix;
+  uint pad_2;
+  uint pad_3;
 };
 
 struct ExternalTextureParams_std140 {
   uint numPlanes;
   uint doYuvToRgbConversionOnly;
+  uint pad;
+  uint pad_1;
   mat3x4 yuvToRgbConversionMatrix;
   GammaTransferParams gammaDecodeParams;
   GammaTransferParams gammaEncodeParams;
@@ -117,6 +131,8 @@
   vec2 coordTransformationMatrix_0;
   vec2 coordTransformationMatrix_1;
   vec2 coordTransformationMatrix_2;
+  uint pad_2;
+  uint pad_3;
 };
 
 layout(binding = 2, std140) uniform ext_tex_params_block_std140_ubo {
@@ -149,7 +165,7 @@
 uniform highp sampler2D arg_0_1;
 uniform highp sampler2D ext_tex_plane_1_1;
 ExternalTextureParams conv_ExternalTextureParams(ExternalTextureParams_std140 val) {
-  return ExternalTextureParams(val.numPlanes, val.doYuvToRgbConversionOnly, val.yuvToRgbConversionMatrix, val.gammaDecodeParams, val.gammaEncodeParams, val.gamutConversionMatrix, mat3x2(val.coordTransformationMatrix_0, val.coordTransformationMatrix_1, val.coordTransformationMatrix_2));
+  return ExternalTextureParams(val.numPlanes, val.doYuvToRgbConversionOnly, val.pad, val.pad_1, val.yuvToRgbConversionMatrix, val.gammaDecodeParams, val.gammaEncodeParams, val.gamutConversionMatrix, mat3x2(val.coordTransformationMatrix_0, val.coordTransformationMatrix_1, val.coordTransformationMatrix_2), val.pad_2, val.pad_3);
 }
 
 void textureLoad_1bfdfb() {
@@ -180,16 +196,22 @@
 struct ExternalTextureParams {
   uint numPlanes;
   uint doYuvToRgbConversionOnly;
+  uint pad;
+  uint pad_1;
   mat3x4 yuvToRgbConversionMatrix;
   GammaTransferParams gammaDecodeParams;
   GammaTransferParams gammaEncodeParams;
   mat3 gamutConversionMatrix;
   mat3x2 coordTransformationMatrix;
+  uint pad_2;
+  uint pad_3;
 };
 
 struct ExternalTextureParams_std140 {
   uint numPlanes;
   uint doYuvToRgbConversionOnly;
+  uint pad;
+  uint pad_1;
   mat3x4 yuvToRgbConversionMatrix;
   GammaTransferParams gammaDecodeParams;
   GammaTransferParams gammaEncodeParams;
@@ -197,6 +219,8 @@
   vec2 coordTransformationMatrix_0;
   vec2 coordTransformationMatrix_1;
   vec2 coordTransformationMatrix_2;
+  uint pad_2;
+  uint pad_3;
 };
 
 layout(binding = 2, std140) uniform ext_tex_params_block_std140_ubo {
@@ -229,7 +253,7 @@
 uniform highp sampler2D arg_0_1;
 uniform highp sampler2D ext_tex_plane_1_1;
 ExternalTextureParams conv_ExternalTextureParams(ExternalTextureParams_std140 val) {
-  return ExternalTextureParams(val.numPlanes, val.doYuvToRgbConversionOnly, val.yuvToRgbConversionMatrix, val.gammaDecodeParams, val.gammaEncodeParams, val.gamutConversionMatrix, mat3x2(val.coordTransformationMatrix_0, val.coordTransformationMatrix_1, val.coordTransformationMatrix_2));
+  return ExternalTextureParams(val.numPlanes, val.doYuvToRgbConversionOnly, val.pad, val.pad_1, val.yuvToRgbConversionMatrix, val.gammaDecodeParams, val.gammaEncodeParams, val.gamutConversionMatrix, mat3x2(val.coordTransformationMatrix_0, val.coordTransformationMatrix_1, val.coordTransformationMatrix_2), val.pad_2, val.pad_3);
 }
 
 void textureLoad_1bfdfb() {