Use NV_draw_buffers to implement EXT_draw_buffers

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 e853d9b59387fac65e910d0ca3fb0cdba2fcf157..9ff69100c359bef6ca468cc52150e620288f551a 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -132,6 +132,7 @@ FeatureInfo::FeatureFlags::FeatureFlags()
       enable_shader_name_hashing(false),
       enable_samplers(false),
       ext_draw_buffers(false),
+      nv_draw_buffers(false),
       ext_frag_depth(false),
       ext_shader_texture_lod(false),
       use_async_readpixels(false),
@@ -760,11 +761,15 @@ void FeatureInfo::InitializeFeatures() {
     validators_.vertex_attribute.AddValue(GL_VERTEX_ATTRIB_ARRAY_DIVISOR_ANGLE);
   }
 
+  bool vendor_agnostic_draw_buffers =
+      extensions.Contains("GL_ARB_draw_buffers") ||
+      extensions.Contains("GL_EXT_draw_buffers");
   if (!workarounds_.disable_ext_draw_buffers &&
-      (extensions.Contains("GL_ARB_draw_buffers") ||
-       extensions.Contains("GL_EXT_draw_buffers"))) {
+      (vendor_agnostic_draw_buffers ||
+       (extensions.Contains("GL_NV_draw_buffers") && is_es3))) {
     AddExtensionString("GL_EXT_draw_buffers");
     feature_flags_.ext_draw_buffers = true;
+    feature_flags_.nv_draw_buffers = !vendor_agnostic_draw_buffers;
 
     GLint max_color_attachments = 0;
     glGetIntegerv(GL_MAX_COLOR_ATTACHMENTS_EXT, &max_color_attachments);