Record path memory usage in SkPictures (#18827)

lib/ui/painting/canvas.cc

@@ -181,6 +181,7 @@ void Canvas::clipPath(const CanvasPath* path, bool doAntiAlias) {
   if (!path)
     Dart_ThrowException(
         ToDart("Canvas.clipPath called with non-genuine Path."));
+  external_allocation_size_ += path->path().approximateBytesUsed();
   canvas_->clipPath(path->path(), doAntiAlias);
 }
 
@@ -280,6 +281,7 @@ void Canvas::drawPath(const CanvasPath* path,
   if (!path)
     Dart_ThrowException(
         ToDart("Canvas.drawPath called with non-genuine Path."));
+  external_allocation_size_ += path->path().approximateBytesUsed();
   canvas_->drawPath(path->path(), *paint.paint());
 }
 
@@ -425,6 +427,7 @@ void Canvas::drawShadow(const CanvasPath* path,
         ToDart("Canvas.drawShader called with non-genuine Path."));
   SkScalar dpr =
       UIDartState::Current()->window()->viewport_metrics().device_pixel_ratio;
+  external_allocation_size_ += path->path().approximateBytesUsed();
   flutter::PhysicalShapeLayer::DrawShadow(canvas_, path->path(), color,
                                           elevation, transparentOccluder, dpr);
 }

lib/ui/painting/path.cc

@@ -297,4 +297,11 @@ void CanvasPath::clone(Dart_Handle path_handle) {
   path->path_ = path_;
 }
 
+// This is doomed to be called too early, since Paths are mutable.
+// However, it can help for some of the clone/shift/transform type methods
+// where the resultant path will initially have a meaningful size.
+size_t CanvasPath::GetAllocationSize() const {
+  return sizeof(CanvasPath) + path_.approximateBytesUsed();
+}
+
 }  // namespace flutter

lib/ui/painting/path.h

@@ -110,6 +110,8 @@ class CanvasPath : public RefCountedDartWrappable<CanvasPath> {
 
   const SkPath& path() const { return path_; }
 
+  size_t GetAllocationSize() const override;
+
   static void RegisterNatives(tonic::DartLibraryNatives* natives);
 
  private:

testing/dart/canvas_test.dart

@@ -286,4 +286,23 @@ void main() {
 
     expect(picture2.approximateBytesUsed, greaterThan(minimumExpected));
   });
+
+  test('Path reflected in picture size for drawPath, clipPath, and drawShadow', () async {
+    final PictureRecorder recorder = PictureRecorder();
+    final Canvas canvas = Canvas(recorder);
+    final Path path = Path();
+    for (int i = 0; i < 10000; i++) {
+      path.lineTo(5, 9);
+      path.lineTo(i.toDouble(), i.toDouble());
+    }
+    path.close();
+    canvas.drawPath(path, Paint());
+    canvas.drawShadow(path, const Color(0xFF000000), 5.0, false);
+    canvas.clipPath(path);
+    final Picture picture = recorder.endRecording();
+
+    // Slightly fuzzy here to allow for platform specific differences
+    // Measurement on macOS: 541078
+    expect(picture.approximateBytesUsed, greaterThan(530000));
+  });
 }