Track stage for varying sub-fields (#842)

Fixes #841

This reverts a small change made in #815 that seemed innocent at the time: we stopped tracking an explicit `Stage` to go with every `VarLayout` that is part of an entry-point varying parameter, and instead only associated the stage with the top-level parameter. That change ended up breaking the logic to emit the `flat` modifier automatically for integer type fragment-shader inputs for GLSL, but we didn't have a regression test to catch that case.

This change adds a regression test to cover this case, and adds the small number of lines that were removed from `parameter-binding.cpp`.
A few other test outputs had to be updated for the change (these are outputs that were changed in #815 for the same reason).

1 files changed, 2 insertions, 0 deletions

diff --git a/tests/reflection/sample-rate-input.hlsl.expected b/tests/reflection/sample-rate-input.hlsl.expected
index ec6cfca6e..0c86ebecb 100644
--- a/tests/reflection/sample-rate-input.hlsl.expected
+++ b/tests/reflection/sample-rate-input.hlsl.expected
@@ -29,6 +29,7 @@ standard output = {
                                         "scalarType": "float32"
                                     }
                                 },
+                                "stage": "fragment",
                                 "binding": {"kind": "varyingInput", "index": 0},
                                 "semanticName": "EXTRA"
                             },
@@ -42,6 +43,7 @@ standard output = {
                                         "scalarType": "float32"
                                     }
                                 },
+                                "stage": "fragment",
                                 "binding": {"kind": "varyingInput", "index": 1},
                                 "semanticName": "COLOR"
                             }