In the current implementation, use the same paint with a linear gradient to draw a Rect and a Circle, two Circles will appear on the screen.

fix flutter/flutter#109293

test

TEST_P(AiksTest, CanRenderDifferentShapesWithSameColorSource) {
  Canvas canvas;
  Paint paint;
  paint.color_source = []() {
    auto contents = std::make_shared<LinearGradientContents>();
    contents->SetEndPoints({0, 0}, {100, 100});
    std::vector<Color> colors = {Color{0.9568, 0.2627, 0.2118, 1.0},
                                 Color{0.1294, 0.5882, 0.9529, 1.0}};
    contents->SetColors(std::move(colors));
    contents->SetTileMode(Entity::TileMode::kRepeat);
    return contents;
  };
  canvas.Save();
  canvas.Translate({100, 100, 0});
  canvas.DrawRect({0, 0, 200, 200}, paint);
  canvas.Restore();

  canvas.Save();
  canvas.Translate({100, 400, 0});
  canvas.DrawCircle({100, 100}, 100, paint);
  canvas.Restore();
  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
}

before change

after change

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide] and the [C++, Objective-C, Java style guides].
• I listed at least one issue that this PR fixes in the description above.
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test-exempt. See [testing the engine] for instructions on
  writing and running engine tests.
• I updated/added relevant documentation (doc comments with ///).
• I signed the [CLA].
• All existing and new tests are passing.