fixed impeller golden content scale (#167308)

fixes https://github.com/flutter/flutter/issues/162036

This fixes the problem my scaling the render texture by the content
scalar. This means locally you'll probably be generating 2048x1536
images. This matches the rendering that is happening in playgrounds. On
CI the content scalar should be one so there is no change there.

## Pre-launch Checklist

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there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
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we expect every widget to implement].
- [x] I signed the [CLA].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

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engine/src/flutter/impeller/golden_tests/golden_playground_test_mac.cc

@@ -222,10 +222,16 @@ bool GoldenPlaygroundTest::OpenPlaygroundHere(
   AiksContext renderer(GetContext(), typographer_context_);
 
   std::unique_ptr<testing::Screenshot> screenshot;
+  Point content_scale =
+      pimpl_->screenshotter->GetPlayground().GetContentScale();
+
+  ISize physical_window_size(
+      std::round(pimpl_->window_size.width * content_scale.x),
+      std::round(pimpl_->window_size.height * content_scale.y));
   for (int i = 0; i < 2; ++i) {
     auto display_list = callback();
     auto texture =
-        DisplayListToTexture(display_list, pimpl_->window_size, renderer);
+        DisplayListToTexture(display_list, physical_window_size, renderer);
     screenshot = pimpl_->screenshotter->MakeScreenshot(renderer, texture);
   }
   return SaveScreenshot(std::move(screenshot));
@@ -320,9 +326,14 @@ fml::Status GoldenPlaygroundTest::SetCapabilities(
 std::unique_ptr<testing::Screenshot> GoldenPlaygroundTest::MakeScreenshot(
     const sk_sp<flutter::DisplayList>& list) {
   AiksContext renderer(GetContext(), typographer_context_);
+  Point content_scale =
+      pimpl_->screenshotter->GetPlayground().GetContentScale();
 
+  ISize physical_window_size(
+      std::round(pimpl_->window_size.width * content_scale.x),
+      std::round(pimpl_->window_size.height * content_scale.y));
   return pimpl_->screenshotter->MakeScreenshot(
-      renderer, DisplayListToTexture(list, pimpl_->window_size, renderer));
+      renderer, DisplayListToTexture(list, physical_window_size, renderer));
 }
 
 }  // namespace impeller

engine/src/flutter/impeller/golden_tests/metal_screenshotter.mm

@@ -43,7 +43,7 @@ std::unique_ptr<Screenshot> MetalScreenshotter::MakeScreenshot(
         imageByApplyingOrientation:kCGImagePropertyOrientationDownMirrored];
 
     CGImageRef cgImage = [cicontext createCGImage:flipped
-                                         fromRect:[ciImage extent]];
+                                         fromRect:[flipped extent]];
 
     // NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
     return std::unique_ptr<MetalScreenshot>(new MetalScreenshot(cgImage));