Update embedder.h to the latest version

src/flutter/shell/platform/embedder/embedder.h

@@ -447,6 +447,43 @@ typedef const void* FlutterMetalCommandQueueHandle;
 /// Alias for id<MTLTexture>.
 typedef const void* FlutterMetalTextureHandle;
 
+/// Pixel format for the external texture.
+typedef enum {
+  kYUVA,
+  kRGBA,
+} FlutterMetalExternalTexturePixelFormat;
+
+typedef struct {
+  /// The size of this struct. Must be sizeof(FlutterMetalExternalTexture).
+  size_t struct_size;
+  /// Height of the texture.
+  size_t width;
+  /// Height of the texture.
+  size_t height;
+  /// The pixel format type of the external.
+  FlutterMetalExternalTexturePixelFormat pixel_format;
+  /// Represents the size of the `textures` array.
+  size_t num_textures;
+  /// Supported textures are YUVA and RGBA, in case of YUVA we expect 2 texture
+  /// handles to be provided by the embedder, Y first and UV next. In case of
+  /// RGBA only one should be passed.
+  /// These are individually aliases for id<MTLTexture>. These textures are
+  /// retained by the engine for the period of the composition. Once these
+  /// textures have been unregistered via the
+  /// `FlutterEngineUnregisterExternalTexture`, the embedder has to release
+  /// these textures.
+  FlutterMetalTextureHandle* textures;
+} FlutterMetalExternalTexture;
+
+/// Callback to provide an external texture for a given texture_id.
+/// See: external_texture_frame_callback.
+typedef bool (*FlutterMetalTextureFrameCallback)(
+    void* /* user data */,
+    int64_t /* texture identifier */,
+    size_t /* width */,
+    size_t /* height */,
+    FlutterMetalExternalTexture* /* texture out */);
+
 typedef struct {
   /// The size of this struct. Must be sizeof(FlutterMetalTexture).
   size_t struct_size;
@@ -485,6 +522,11 @@ typedef struct {
   /// The callback presented to the embedder to present a fully populated metal
   /// texture to the user.
   FlutterMetalPresentCallback present_drawable_callback;
+  /// When the embedder specifies that a texture has a frame available, the
+  /// engine will call this method (on an internal engine managed thread) so
+  /// that external texture details can be supplied to the engine for subsequent
+  /// composition.
+  FlutterMetalTextureFrameCallback external_texture_frame_callback;
 } FlutterMetalRendererConfig;
 
 typedef struct {