Implement WEBGL_compressed_texture_s3tc_srgb

gpu/command_buffer/service/feature_info.cc

Index: gpu/command_buffer/service/feature_info.cc
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index f52374aa71631f9e352b8bde72937a022a18bd94..a2b94b7eab74f19b685a52f7527f32269fa6dc33 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -591,11 +591,13 @@ void FeatureInfo::InitializeFeatures() {
   // sized formats GL_SRGB8 and GL_SRGB8_ALPHA8. Also, SRGB_EXT isn't a valid
   // <format> in this case. So, even with GLES3 explicitly check for
   // GL_EXT_sRGB.
+  bool have_srgb = false;
   if ((((gl_version_info_->is_es3 ||
          extensions.Contains("GL_OES_rgb8_rgba8")) &&
         extensions.Contains("GL_EXT_sRGB")) ||
        feature_flags_.desktop_srgb_support) &&
        IsWebGL1OrES2Context()) {
+    have_srgb = true;
     AddExtensionString("GL_EXT_sRGB");
     validators_.texture_internal_format.AddValue(GL_SRGB_EXT);
     validators_.texture_internal_format.AddValue(GL_SRGB_ALPHA_EXT);
@@ -608,6 +610,28 @@ void FeatureInfo::InitializeFeatures() {
     validators_.texture_unsized_internal_format.AddValue(GL_SRGB_ALPHA_EXT);
   }
 
+  if ((have_s3tc || (enable_dxt1 && enable_dxt3 && enable_dxt5)) && have_srgb) {
+    AddExtensionString("GL_EXT_texture_compression_s3tc_srgb");
+
+    validators_.compressed_texture_format.AddValue(
+        GL_COMPRESSED_SRGB_S3TC_DXT1_EXT);
+    validators_.compressed_texture_format.AddValue(
+        GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT);
+    validators_.compressed_texture_format.AddValue(
+        GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT);
+    validators_.compressed_texture_format.AddValue(
+        GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT);
+
+    validators_.texture_internal_format_storage.AddValue(
+        GL_COMPRESSED_SRGB_S3TC_DXT1_EXT);
+    validators_.texture_internal_format_storage.AddValue(
+        GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT);
+    validators_.texture_internal_format_storage.AddValue(
+        GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT);
+    validators_.texture_internal_format_storage.AddValue(
+        GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT);
+  }
+
   // Note: Only APPLE_texture_format_BGRA8888 extension allows BGRA8_EXT in
   // ES3's glTexStorage2D, whereas EXT_texture_format_BGRA8888 doesn't provide
   // that compatibility. So if EXT_texture_format_BGRA8888 (but not