GL: Align emulated ETC1 handling with other backends

src/libANGLE/renderer/gl/formatutilsgl.cpp

@@ -349,7 +349,7 @@ static InternalFormatInfoMap BuildInternalFormatInfoMap()
     InsertFormatMapping(&map, GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT, ExtAndVersionOrExt("GL_EXT_texture_compression_s3tc", 2, 1, "GL_EXT_texture_sRGB"), AlwaysSupported(), NeverSupported(), ExtsOnly("GL_EXT_texture_compression_s3tc_srgb", "GL_EXT_texture_compression_s3tc GL_NV_sRGB_formats"), AlwaysSupported(), NeverSupported(),                      NeverSupported()                );
 
     // From GL_OES_compressed_ETC1_RGB8_texture
-    InsertFormatMapping(&map, GL_ETC1_RGB8_OES,                   NeverSupported(), NeverSupported(), NeverSupported(), VersionOrExts(3, 0, "GL_OES_compressed_ETC1_RGB8_texture"),       AlwaysSupported(), NeverSupported(),                      NeverSupported()                );
+    InsertFormatMapping(&map, GL_ETC1_RGB8_OES,                   VersionOrExts(4, 3, "GL_ARB_ES3_compatibility"), AlwaysSupported(), NeverSupported(), VersionOrExts(3, 0, "GL_OES_compressed_ETC1_RGB8_texture"),       AlwaysSupported(), NeverSupported(),                      NeverSupported()                );
 
     // From GL_OES_texture_compression_astc
     //                       | Format                                   | OpenGL texture                                 | Filter           | Render          | OpenGL ES texture support                      | Filter           | ES attachment   | ES renderbuffer |

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -1679,6 +1679,11 @@ void GenerateCaps(const FunctionsGL *functions,
         (features.allowEtcFormats.enabled || functions->standard == STANDARD_GL_ES) &&
         gl::DetermineCompressedTextureETCSupport(*textureCapsMap);
 
+    // When running on top of desktop OpenGL drivers and allow_etc_formats feature is not enabled,
+    // mark ETC1 as emulated to hide it from WebGL clients.
+    limitations->emulatedEtc1 =
+        !features.allowEtcFormats.enabled && functions->standard == STANDARD_GL_DESKTOP;
+
     // To work around broken unsized sRGB textures, sized sRGB textures are used. Disable EXT_sRGB
     // if those formats are not available.
     if (features.unsizedsRGBReadPixelsDoesntTransform.enabled &&