Phase 5E: remove legacy shader string wrapper

Author: mark-ik

webrender_build/src/shader.rs

@@ -111,36 +111,6 @@ pub fn shader_source_from_file(shader_path: &Path) -> String {
     source
 }
 
-/// Creates heap-allocated strings for both vertex and fragment shaders.
-pub fn build_shader_strings<G: Fn(&str) -> Cow<'static, str>>(
-    gl_version: ShaderVersion,
-    features: &[&str],
-    base_filename: &str,
-    get_source: &G,
-) -> (String, String) {
-    let mut vs_source = String::new();
-    do_build_shader_string(
-        gl_version,
-        features,
-        ShaderKind::Vertex,
-        base_filename,
-        get_source,
-        |s| vs_source.push_str(s),
-    );
-
-    let mut fs_source = String::new();
-    do_build_shader_string(
-        gl_version,
-        features,
-        ShaderKind::Fragment,
-        base_filename,
-        get_source,
-        |s| fs_source.push_str(s),
-    );
-
-    (vs_source, fs_source)
-}
-
 /// Walks the given shader string and applies the output to the provided
 /// callback. Assuming an override path is not used, does no heap allocation
 /// and no I/O.

wr-wgpu-notes/2026-04-18_spirv_shader_pipeline_plan.md

@@ -473,6 +473,10 @@ Validation should follow the canonical artifact graph.
   `webrender_build/tests/generated_output_validation.rs`, while Wrench keeps
   exercising runtime shader compilation through its normal GL initialization and
   parity lanes.
+- the full vertex+fragment legacy GLSL string assembly wrapper is gone as well.
+  Remaining legacy GLSL users call the lower-level streaming prefix/main helpers
+  directly, which keeps `gpu_cache_update` and explicit shader override loading
+  working without preserving the old validator-oriented full-corpus API.
 
 #### Current branch status