Updated the wide-gamut constant and added a unit test for it. (#39776)

* Updated the wide-gamut constant and added a unit test for it.

* dan feedback

Author: gaaclarke

lib/ui/painting/image_decoder_impeller.cc

@@ -49,7 +49,8 @@ float CalculateArea(SkPoint abc[3]) {
                       b.fX * a.fY);
 }
 
-static constexpr float kSrgbD50GamutArea = 0.084f;
+// Note: This was calculated from SkColorSpace::MakeSRGB().
+static constexpr float kSrgbGamutArea = 0.0982f;
 
 // Source:
 // https://source.chromium.org/chromium/_/skia/skia.git/+/393fb1ec80f41d8ad7d104921b6920e69749fda1:src/codec/SkAndroidCodec.cpp;l=67;drc=46572b4d445f41943059d0e377afc6d6748cd5ca;bpv=1;bpt=0
@@ -58,7 +59,8 @@ bool IsWideGamut(const SkColorSpace& color_space) {
   color_space.toXYZD50(&xyzd50);
   SkPoint rgb[3];
   LoadGamut(rgb, xyzd50);
-  return CalculateArea(rgb) > kSrgbD50GamutArea;
+  float area = CalculateArea(rgb);
+  return area > kSrgbGamutArea;
 }
 }  // namespace
 

lib/ui/painting/image_decoder_unittests.cc

@@ -333,6 +333,28 @@ TEST_F(ImageDecoderFixtureTest, ImpellerWideGamutDisplayP3) {
 #endif  // IMPELLER_SUPPORTS_RENDERING
 }
 
+TEST_F(ImageDecoderFixtureTest, ImpellerNonWideGamut) {
+  auto data = OpenFixtureAsSkData("Horizontal.jpg");
+  auto image = SkImage::MakeFromEncoded(data);
+  ASSERT_TRUE(image != nullptr);
+  ASSERT_EQ(SkISize::Make(600, 200), image->dimensions());
+
+  ImageGeneratorRegistry registry;
+  std::shared_ptr<ImageGenerator> generator =
+      registry.CreateCompatibleGenerator(data);
+  ASSERT_TRUE(generator);
+
+  auto descriptor = fml::MakeRefCounted<ImageDescriptor>(std::move(data),
+                                                         std::move(generator));
+
+#if IMPELLER_SUPPORTS_RENDERING
+  std::shared_ptr<SkBitmap> bitmap = ImageDecoderImpeller::DecompressTexture(
+      descriptor.get(), SkISize::Make(600, 200), {600, 200},
+      /*supports_wide_gamut=*/true);
+  ASSERT_EQ(bitmap->colorType(), kRGBA_8888_SkColorType);
+#endif  // IMPELLER_SUPPORTS_RENDERING
+}
+
 TEST_F(ImageDecoderFixtureTest, ExifDataIsRespectedOnDecode) {
   auto loop = fml::ConcurrentMessageLoop::Create();
   TaskRunners runners(GetCurrentTestName(),         // label