Break Layer class into Gl and Vulkan subclasses

Test: manual testing
Change-Id: Ibd2beed39de3ac6da7448e96496253cfe427dfbb
diff --git a/libs/hwui/GlopBuilder.h b/libs/hwui/GlopBuilder.h
index 8a8b652..87b1568 100644
--- a/libs/hwui/GlopBuilder.h
+++ b/libs/hwui/GlopBuilder.h
@@ -28,6 +28,7 @@
 namespace uirenderer {
 
 class Caches;
+class GlLayer;
 class Matrix4;
 class Patch;
 class RenderState;
@@ -71,7 +72,7 @@
     GlopBuilder& setFillClear();
     GlopBuilder& setFillLayer(Texture& texture, const SkColorFilter* colorFilter,
             float alpha, SkBlendMode mode, Blend::ModeOrderSwap modeUsage);
-    GlopBuilder& setFillTextureLayer(Layer& layer, float alpha);
+    GlopBuilder& setFillTextureLayer(GlLayer& layer, float alpha);
     // TODO: setFillLayer normally forces its own wrap & filter mode,
     // which isn't always correct.
     GlopBuilder& setFillExternalTexture(Texture& texture, Matrix4& textureTransform);