[Impeller] Set color attachment pixel format to RGBA on OpenGLES backend (#37843)

impeller/renderer/backend/gles/context_gles.cc

diff --git a/impeller/renderer/backend/gles/context_gles.cc b/impeller/renderer/backend/gles/context_gles.cc
index e539249..9ecd91c 100644
--- a/impeller/renderer/backend/gles/context_gles.cc
+++ b/impeller/renderer/backend/gles/context_gles.cc
@@ -142,4 +142,9 @@
   return kLegacyBackendFeatures;
 }
 
+// |Context|
+PixelFormat ContextGLES::GetColorAttachmentPixelFormat() const {
+  return PixelFormat::kR8G8B8A8UNormInt;
+}
+
 }  // namespace impeller

impeller/renderer/backend/gles/context_gles.h

diff --git a/impeller/renderer/backend/gles/context_gles.h b/impeller/renderer/backend/gles/context_gles.h
index 9e23e19..4c84146 100644
--- a/impeller/renderer/backend/gles/context_gles.h
+++ b/impeller/renderer/backend/gles/context_gles.h
@@ -76,6 +76,9 @@
   // |Context|
   const BackendFeatures& GetBackendFeatures() const override;
 
+  // |Context|
+  PixelFormat GetColorAttachmentPixelFormat() const override;
+
   FML_DISALLOW_COPY_AND_ASSIGN(ContextGLES);
 };
 

impeller/renderer/render_target.cc

diff --git a/impeller/renderer/render_target.cc b/impeller/renderer/render_target.cc
index ef196a0..7c13412 100644
--- a/impeller/renderer/render_target.cc
+++ b/impeller/renderer/render_target.cc
@@ -192,7 +192,7 @@
 
   TextureDescriptor color_tex0;
   color_tex0.storage_mode = color_storage_mode;
-  color_tex0.format = PixelFormat::kDefaultColor;
+  color_tex0.format = context.GetColorAttachmentPixelFormat();
   color_tex0.size = size;
   color_tex0.usage = static_cast<uint64_t>(TextureUsage::kRenderTarget) |
                      static_cast<uint64_t>(TextureUsage::kShaderRead);
@@ -257,7 +257,7 @@
   color0_tex_desc.storage_mode = color_storage_mode;
   color0_tex_desc.type = TextureType::kTexture2DMultisample;
   color0_tex_desc.sample_count = SampleCount::kCount4;
-  color0_tex_desc.format = PixelFormat::kDefaultColor;
+  color0_tex_desc.format = context.GetColorAttachmentPixelFormat();
   color0_tex_desc.size = size;
   color0_tex_desc.usage = static_cast<uint64_t>(TextureUsage::kRenderTarget);
 
@@ -274,7 +274,7 @@
 
   TextureDescriptor color0_resolve_tex_desc;
   color0_resolve_tex_desc.storage_mode = color_resolve_storage_mode;
-  color0_resolve_tex_desc.format = PixelFormat::kDefaultColor;
+  color0_resolve_tex_desc.format = context.GetColorAttachmentPixelFormat();
   color0_resolve_tex_desc.size = size;
   color0_resolve_tex_desc.usage =
       static_cast<uint64_t>(TextureUsage::kRenderTarget) |