Reland: [Impeller] Turned on new blur. (flutter#48472) (flutter#49642)

This is a reland of the new gaussian blur.

Changes since revert:
1) Textures are now recycled with ping ponging to reduce memory usage
1) Mipmaps are generated to diminish the shimmering that happens with animated blurs (in metal)

---

This new blur should perform faster since it scales down the image before blurring it. Jonah did early testing of it and found it to be faster. Scrolling around with the blur perf bug it seems faster. It also has a wider test bed and is hopefully easier to maintain since it contains all of its logic for both directions.

testing: There are existing blur tests and we've backfilled more as we've added features to this blur.

fixes flutter/flutter#131580 fixes flutter/flutter#138259

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impeller/aiks/aiks_unittests.cc

@@ -3758,10 +3758,13 @@ TEST_P(AiksTest, GaussianBlurSetsMipCountOnPass) {
   canvas.Restore();
 
   Picture picture = canvas.EndRecordingAsPicture();
-  EXPECT_EQ(1, picture.pass->GetRequiredMipCount());
+  EXPECT_EQ(4, picture.pass->GetRequiredMipCount());
 }
 
 TEST_P(AiksTest, GaussianBlurAllocatesCorrectMipCountRenderTarget) {
+  size_t blur_required_mip_count =
+      GetParam() == PlaygroundBackend::kMetal ? 4 : 1;
+
   Canvas canvas;
   canvas.DrawCircle({100, 100}, 50, {.color = Color::CornflowerBlue()});
   canvas.SaveLayer({}, std::nullopt,
@@ -3782,11 +3785,14 @@ TEST_P(AiksTest, GaussianBlurAllocatesCorrectMipCountRenderTarget) {
     max_mip_count =
         std::max(it->texture->GetTextureDescriptor().mip_count, max_mip_count);
   }
-  EXPECT_EQ(max_mip_count, 1lu);
+  EXPECT_EQ(max_mip_count, blur_required_mip_count);
 }
 
 TEST_P(AiksTest, GaussianBlurMipMapNestedLayer) {
   fml::testing::LogCapture log_capture;
+  size_t blur_required_mip_count =
+      GetParam() == PlaygroundBackend::kMetal ? 4 : 1;
+
   Canvas canvas;
   canvas.DrawPaint({.color = Color::Wheat()});
   canvas.SaveLayer({.blend_mode = BlendMode::kMultiply});
@@ -3809,12 +3815,19 @@ TEST_P(AiksTest, GaussianBlurMipMapNestedLayer) {
     max_mip_count =
         std::max(it->texture->GetTextureDescriptor().mip_count, max_mip_count);
   }
-  EXPECT_EQ(max_mip_count, 1lu);
-  EXPECT_EQ(log_capture.str().find(GaussianBlurFilterContents::kNoMipsError),
-            std::string::npos);
+  EXPECT_EQ(max_mip_count, blur_required_mip_count);
+  if (GetParam() == PlaygroundBackend::kMetal) {
+    EXPECT_EQ(log_capture.str().find(GaussianBlurFilterContents::kNoMipsError),
+              std::string::npos);
+  } else {
+    EXPECT_NE(log_capture.str().find(GaussianBlurFilterContents::kNoMipsError),
+              std::string::npos);
+  }
 }
 
 TEST_P(AiksTest, GaussianBlurMipMapImageFilter) {
+  size_t blur_required_mip_count =
+      GetParam() == PlaygroundBackend::kMetal ? 4 : 1;
   fml::testing::LogCapture log_capture;
   Canvas canvas;
   canvas.SaveLayer(
@@ -3835,9 +3848,14 @@ TEST_P(AiksTest, GaussianBlurMipMapImageFilter) {
     max_mip_count =
         std::max(it->texture->GetTextureDescriptor().mip_count, max_mip_count);
   }
-  EXPECT_EQ(max_mip_count, 1lu);
-  EXPECT_EQ(log_capture.str().find(GaussianBlurFilterContents::kNoMipsError),
-            std::string::npos);
+  EXPECT_EQ(max_mip_count, blur_required_mip_count);
+  if (GetParam() == PlaygroundBackend::kMetal) {
+    EXPECT_EQ(log_capture.str().find(GaussianBlurFilterContents::kNoMipsError),
+              std::string::npos);
+  } else {
+    EXPECT_NE(log_capture.str().find(GaussianBlurFilterContents::kNoMipsError),
+              std::string::npos);
+  }
 }
 
 }  // namespace testing

impeller/entity/contents/filters/directional_gaussian_blur_filter_contents.h

@@ -43,6 +43,9 @@ namespace impeller {
 ///   - `FilterContents::MakeGaussianBlur`
 ///   - //flutter/impeller/entity/shaders/gaussian_blur/gaussian_blur.glsl
 ///
+///\deprecated Previously 2 of these were chained to do 2D blurs, use
+///            \ref GaussianBlurFilterContents instead since it has better
+///            performance.
 class DirectionalGaussianBlurFilterContents final : public FilterContents {
  public:
   DirectionalGaussianBlurFilterContents();

impeller/entity/contents/filters/filter_contents.cc

@@ -50,50 +50,18 @@ std::shared_ptr<FilterContents> FilterContents::MakeDirectionalGaussianBlur(
   return blur;
 }
 
-#ifdef IMPELLER_ENABLE_NEW_GAUSSIAN_FILTER
 const int32_t FilterContents::kBlurFilterRequiredMipCount = 4;
-#else
-const int32_t FilterContents::kBlurFilterRequiredMipCount = 1;
-#endif
 
 std::shared_ptr<FilterContents> FilterContents::MakeGaussianBlur(
     const FilterInput::Ref& input,
     Sigma sigma_x,
     Sigma sigma_y,
     BlurStyle blur_style,
     Entity::TileMode tile_mode) {
-  constexpr bool use_new_filter =
-#ifdef IMPELLER_ENABLE_NEW_GAUSSIAN_FILTER
-      true;
-#else
-      false;
-#endif
-
-  // TODO(https://github.com/flutter/flutter/issues/131580): Remove once the new
-  // blur handles all cases.
-  if (use_new_filter) {
-    auto blur = std::make_shared<GaussianBlurFilterContents>(
-        sigma_x.sigma, sigma_y.sigma, tile_mode);
-    blur->SetInputs({input});
-    return blur;
-  }
-  std::shared_ptr<FilterContents> x_blur = MakeDirectionalGaussianBlur(
-      /*input=*/input,
-      /*sigma=*/sigma_x,
-      /*direction=*/Point(1, 0),
-      /*blur_style=*/BlurStyle::kNormal,
-      /*tile_mode=*/tile_mode,
-      /*is_second_pass=*/false,
-      /*secondary_sigma=*/{});
-  std::shared_ptr<FilterContents> y_blur = MakeDirectionalGaussianBlur(
-      /*input=*/FilterInput::Make(x_blur),
-      /*sigma=*/sigma_y,
-      /*direction=*/Point(0, 1),
-      /*blur_style=*/blur_style,
-      /*tile_mode=*/tile_mode,
-      /*is_second_pass=*/true,
-      /*secondary_sigma=*/sigma_x);
-  return y_blur;
+  auto blur = std::make_shared<GaussianBlurFilterContents>(
+      sigma_x.sigma, sigma_y.sigma, tile_mode);
+  blur->SetInputs({input});
+  return blur;
 }
 
 std::shared_ptr<FilterContents> FilterContents::MakeBorderMaskBlur(

impeller/entity/entity_pass.cc

@@ -256,6 +256,14 @@ static EntityPassTarget CreateRenderTarget(ContentContext& renderer,
   /// What's important is the `StorageMode` of the textures, which cannot be
   /// changed for the lifetime of the textures.
 
+  if (context->GetBackendType() != Context::BackendType::kMetal) {
+    // TODO(https://github.com/flutter/flutter/issues/141495): Implement mip map
+    // generation on vulkan.
+    // TODO(https://github.com/flutter/flutter/issues/141732): Implement mip map
+    // generation on opengles.
+    mip_count = 1;
+  }
+
   RenderTarget target;
   if (context->GetCapabilities()->SupportsOffscreenMSAA()) {
     target = RenderTarget::CreateOffscreenMSAA(