command_buffer: Implement EXT_blend_func_extended

gpu/command_buffer/service/disk_cache_proto.proto

 syntax = "proto2";
 option optimize_for = LITE_RUNTIME;
 
 message ShaderVariableProto {
   optional uint32 type = 1;
   optional uint32 precision = 2;
   optional string name = 3;
   optional string mapped_name = 4;
   optional uint32 array_size = 5;
   optional bool static_use = 6;
@@ skipping 14 matching lines @@
   optional ShaderVariableProto basic = 1;
   optional int32 interpolation = 2;
   optional bool is_invariant = 3;
 }
 
 message ShaderProto {
   optional bytes sha = 1;
   repeated ShaderAttributeProto attribs = 2;
   repeated ShaderUniformProto uniforms = 3;
   repeated ShaderVaryingProto varyings = 4;
+  repeated ShaderAttributeProto output_variables = 5;

[Zhenyao Mo, 2015/08/31 21:12:30]

Have you verified what are the returned values for ShGetOutputVariables() in
ES2? Are they empty or gl_FragColor/gl_FragData?

[Kimmo Kinnunen, 2015/09/24 13:16:27]

Yeah, I implemented it in ANGLE for purposes of this patch.

For vertex shaders, it's empty. I can fix it to be whatever you want, if we need
vertex outputs for consistency.

For fragment shaders, it might contain gl_FragColor, gl_FragData,
gl_SecondaryFragColor, gl_SecondaryFragData, gl_FragDepthEXT.

[Zhenyao Mo, 2015/09/30 00:23:47]

Sounds good.

 }
 
 message GpuProgramProto {
   optional bytes sha = 1;
   optional uint32 format = 2;
   optional bytes program = 3;
 
   optional ShaderProto vertex_shader = 4;
   optional ShaderProto fragment_shader = 5;
 }