[Tizen][impeller] Use GLES2 shaders in GL embedder surface

The '[Tizen][impeller] Disable gles3 compile' patch removes generation of
the GLES3 impeller shader variants. Flutter 3.44 changed
embedder_surface_gl_impeller.cc to select GLES3 shaders at runtime, which
fails to compile/link without the GLES3 shader symbols.

Always use the GLES2 shader set (valid on GLES3 contexts as well) so the
GL-only Tizen engine builds with GLES3 shader compilation disabled.

Author: JSUYA

engine/src/flutter/shell/platform/embedder/embedder_surface_gl_impeller.cc

@@ -10,29 +10,16 @@
 #include "impeller/entity/gles/entity_shaders_gles.h"
 #include "impeller/entity/gles/framebuffer_blend_shaders_gles.h"
 #include "impeller/entity/gles/modern_shaders_gles.h"
-#include "impeller/entity/gles3/entity_shaders_gles.h"
-#include "impeller/entity/gles3/framebuffer_blend_shaders_gles.h"
-#include "impeller/entity/gles3/modern_shaders_gles.h"
 #include "impeller/renderer/backend/gles/context_gles.h"
 #include "impeller/renderer/backend/gles/proc_table_gles.h"
 
 namespace flutter {
 
 namespace {
-std::vector<std::shared_ptr<fml::Mapping>> GetShaderMappings(bool is_gles3) {
-  if (is_gles3) {
-    return {
-        std::make_shared<fml::NonOwnedMapping>(
-            impeller_entity_shaders_gles3_data,
-            impeller_entity_shaders_gles3_length),
-        std::make_shared<fml::NonOwnedMapping>(
-            impeller_modern_shaders_gles3_data,
-            impeller_modern_shaders_gles3_length),
-        std::make_shared<fml::NonOwnedMapping>(
-            impeller_framebuffer_blend_shaders_gles3_data,
-            impeller_framebuffer_blend_shaders_gles3_length),
-    };
-  }
+std::vector<std::shared_ptr<fml::Mapping>> GetShaderMappings() {
+  // Tizen: GLES3 impeller shaders are not compiled (see
+  // impeller/tools/shaders.gni). Always use the GLES2 shader set, which is
+  // also valid on GLES3 contexts.
   return {
       std::make_shared<fml::NonOwnedMapping>(
           impeller_entity_shaders_gles_data,
@@ -101,9 +88,7 @@ EmbedderSurfaceGLImpeller::EmbedderSurfaceGLImpeller(
     return;
   }
 
-  const auto is_gles3 =
-      gl->GetDescription()->GetGlVersion().IsAtLeast(impeller::Version(3));
-  const auto shader_mappings = GetShaderMappings(is_gles3);
+  const auto shader_mappings = GetShaderMappings();
 
   impeller_context_ = impeller::ContextGLES::Create(
       impeller::Flags{}, std::move(gl), shader_mappings,