[Impeller] Remove Skia dependency from the impeller/image interface (flutter/engine#40403)

* [Impeller] Remove Skia dependency from the impeller/image interface

* Separate Skia backend target

engine/src/flutter/impeller/BUILD.gn

@@ -54,7 +54,7 @@ group("impeller") {
       "aiks",
       "display_list",
       "entity",
-      "image",
+      "image:image_skia_backend",
       "renderer",
       "renderer/backend",
       "typographer",

engine/src/flutter/impeller/entity/BUILD.gn

@@ -217,7 +217,7 @@ impeller_component("entity") {
     ":framebuffer_blend_entity_shaders",
     ":modern_entity_shaders",
     "../archivist",
-    "../image",
+    "../image:image_skia_backend",
     "../renderer",
     "../scene",
     "../typographer",

engine/src/flutter/impeller/image/BUILD.gn

@@ -11,8 +11,6 @@ impeller_component("image") {
   ]
 
   sources = [
-    "backends/skia/compressed_image_skia.cc",
-    "backends/skia/compressed_image_skia.h",
     "compressed_image.cc",
     "decompressed_image.cc",
   ]
@@ -22,6 +20,20 @@ impeller_component("image") {
     "../geometry",
   ]
 
+  deps = [ "//flutter/fml" ]
+}
+
+impeller_component("image_skia_backend") {
+  public = [ "backends/skia/compressed_image_skia.h" ]
+
+  sources = [ "backends/skia/compressed_image_skia.cc" ]
+
+  public_deps = [
+    ":image",
+    "../base",
+    "../geometry",
+  ]
+
   deps = [
     "//flutter/fml",
     "//third_party/skia",
@@ -32,7 +44,7 @@ impeller_component("image_unittests") {
   testonly = true
   sources = []
   deps = [
-    ":image",
+    ":image_skia_backend",
     "//flutter/testing",
   ]
 }

engine/src/flutter/impeller/image/backends/skia/compressed_image_skia.cc

@@ -14,6 +14,15 @@
 
 namespace impeller {
 
+std::shared_ptr<CompressedImage> CompressedImageSkia::Create(
+    std::shared_ptr<const fml::Mapping> allocation) {
+  // There is only one backend today.
+  if (!allocation) {
+    return nullptr;
+  }
+  return std::make_shared<CompressedImageSkia>(std::move(allocation));
+}
+
 CompressedImageSkia::CompressedImageSkia(
     std::shared_ptr<const fml::Mapping> allocation)
     : CompressedImage(std::move(allocation)) {}

engine/src/flutter/impeller/image/backends/skia/compressed_image_skia.h

@@ -11,6 +11,9 @@ namespace impeller {
 
 class CompressedImageSkia final : public CompressedImage {
  public:
+  static std::shared_ptr<CompressedImage> Create(
+      std::shared_ptr<const fml::Mapping> allocation);
+
   CompressedImageSkia(std::shared_ptr<const fml::Mapping> allocation);
 
   ~CompressedImageSkia() override;

engine/src/flutter/impeller/image/compressed_image.cc

@@ -4,19 +4,8 @@
 
 #include "impeller/image/compressed_image.h"
 
-#include "impeller/image/backends/skia/compressed_image_skia.h"
-
 namespace impeller {
 
-std::shared_ptr<CompressedImage> CompressedImage::Create(
-    std::shared_ptr<const fml::Mapping> allocation) {
-  // There is only one backend today.
-  if (!allocation) {
-    return nullptr;
-  }
-  return std::make_shared<CompressedImageSkia>(std::move(allocation));
-}
-
 CompressedImage::CompressedImage(std::shared_ptr<const fml::Mapping> allocation)
     : source_(std::move(allocation)) {}
 

engine/src/flutter/impeller/image/compressed_image.h

@@ -17,9 +17,6 @@ class ImageSource;
 
 class CompressedImage {
  public:
-  static std::shared_ptr<CompressedImage> Create(
-      std::shared_ptr<const fml::Mapping> allocation);
-
   virtual ~CompressedImage();
 
   [[nodiscard]] virtual DecompressedImage Decode() const = 0;

engine/src/flutter/impeller/playground/BUILD.gn

@@ -45,6 +45,7 @@ impeller_component("playground") {
     "../entity:framebuffer_blend_entity_shaders",
     "../entity:modern_entity_shaders",
     "../fixtures:shader_fixtures",
+    "../image:image_skia_backend",
     "../renderer",
     "../scene/shaders",
     "imgui:imgui_impeller_backend",

engine/src/flutter/impeller/playground/playground.cc

@@ -8,6 +8,7 @@
 #include <sstream>
 
 #include "fml/time/time_point.h"
+#include "impeller/image/backends/skia/compressed_image_skia.h"
 #include "impeller/image/decompressed_image.h"
 #include "impeller/renderer/command_buffer.h"
 #include "impeller/runtime_stage/runtime_stage.h"
@@ -340,7 +341,7 @@ bool Playground::OpenPlaygroundHere(SinglePassCallback pass_callback) {
 
 std::shared_ptr<CompressedImage> Playground::LoadFixtureImageCompressed(
     std::shared_ptr<fml::Mapping> mapping) const {
-  auto compressed_image = CompressedImage::Create(std::move(mapping));
+  auto compressed_image = CompressedImageSkia::Create(std::move(mapping));
   if (!compressed_image) {
     VALIDATION_LOG << "Could not create compressed image.";
     return nullptr;