command_buffer: MAX/BASE_LEVEL fixes for GetTexParameter

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 03a2a4fdad2bf1a201aca6c4808f7735a2b640cb..e7d50e68097fafc368942bc8363289375303b730 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -9270,6 +9270,23 @@ void GLES2DecoderImpl::GetTexParameterImpl(
         return;
       }
       break;
+    // Get the level information from the texture to avoid a Mac driver
+    // bug where they store the levels in int16_t, making values bigger
+    // than 2^15-1 overflow in the negative range.

[Zhenyao Mo, 2016/05/27 22:33:44]

Could you put this code behind a workaround? say, use_shadowed_tex_params?

This way we can turn it off and show driver vendors their bugs.

+    case GL_TEXTURE_BASE_LEVEL:
+      if (fparams) {
+        fparams[0] = static_cast<GLfloat>(texture->base_level());
+      } else {
+        iparams[0] = texture->base_level();
+      }
+      return;
+    case GL_TEXTURE_MAX_LEVEL:
+      if (fparams) {
+        fparams[0] = static_cast<GLfloat>(texture->max_level());
+      } else {
+        iparams[0] = texture->max_level();
+      }
+      return;
     default:
       break;
   }