[macOS] Fix arm64 floating-point test failure (flutter#41228)

FlutterMutatorViewTest.TransformedFrameIsCorrect and
FlutterMutatorViewTest.RoundRectClipsToPath both apply transforms then
do exact comparisons on the resulting 4x4 matrices of CGFloat values.

There are very small differences between the elements in the resulting
matrices, on the order of 1e-15, depending on the CPU architecture on
which the floating point operations were run.

Similar to elsewhere in the framework and engine, we now perform
floating point equality tests within some small error bound -- I've
arbitrarily selected 1e-10.

Issue: flutter/flutter#124840

shell/platform/darwin/macos/framework/Source/FlutterMutatorViewTest.mm

@@ -39,6 +39,34 @@ void ApplyFlutterLayer(FlutterMutatorView* view,
 
   [view applyFlutterLayer:&layer];
 }
+
+// Expect that each element within two CATransform3Ds is within an error bound.
+//
+// In order to avoid architecture-specific floating point differences we don't check for exact
+// equality using, for example, CATransform3DEqualToTransform.
+void ExpectTransform3DEqual(const CATransform3D& t, const CATransform3D& u) {
+  constexpr float kMaxErr = 1e-10;
+
+  EXPECT_NEAR(t.m11, u.m11, kMaxErr);
+  EXPECT_NEAR(t.m12, u.m12, kMaxErr);
+  EXPECT_NEAR(t.m13, u.m13, kMaxErr);
+  EXPECT_NEAR(t.m14, u.m14, kMaxErr);
+
+  EXPECT_NEAR(t.m21, u.m21, kMaxErr);
+  EXPECT_NEAR(t.m22, u.m22, kMaxErr);
+  EXPECT_NEAR(t.m23, u.m23, kMaxErr);
+  EXPECT_NEAR(t.m24, u.m24, kMaxErr);
+
+  EXPECT_NEAR(t.m31, u.m31, kMaxErr);
+  EXPECT_NEAR(t.m32, u.m32, kMaxErr);
+  EXPECT_NEAR(t.m33, u.m33, kMaxErr);
+  EXPECT_NEAR(t.m34, u.m34, kMaxErr);
+
+  EXPECT_NEAR(t.m41, u.m41, kMaxErr);
+  EXPECT_NEAR(t.m42, u.m42, kMaxErr);
+  EXPECT_NEAR(t.m43, u.m43, kMaxErr);
+  EXPECT_NEAR(t.m44, u.m44, kMaxErr);
+}
 }  // namespace
 
 TEST(FlutterMutatorViewTest, BasicFrameIsCorrect) {
@@ -111,9 +139,9 @@ void ApplyFlutterLayer(FlutterMutatorView* view,
   ApplyFlutterLayer(mutatorView, FlutterSize{30 * 2, 20 * 2}, mutations);
   EXPECT_TRUE(CGRectEqualToRect(mutatorView.frame, CGRectMake(92.5, 45, 45, 30)));
   EXPECT_TRUE(CGRectEqualToRect(platformView.frame, CGRectMake(0, 0, 30, 20)));
-  EXPECT_TRUE(
-      CATransform3DEqualToTransform(mutatorView.platformViewContainer.layer.sublayerTransform,
-                                    CATransform3DMakeScale(1.5, 1.5, 1)));
+
+  ExpectTransform3DEqual(mutatorView.platformViewContainer.layer.sublayerTransform,
+                         CATransform3DMakeScale(1.5, 1.5, 1));
 }
 
 TEST(FlutterMutatorViewTest, FrameWithLooseClipIsCorrect) {
@@ -308,9 +336,8 @@ void ApplyFlutterLayer(FlutterMutatorView* view,
       CGRectEqualToRect(mutatorView.subviews.firstObject.frame, CGRectMake(-10, -10, 30, 20)));
   EXPECT_TRUE(CGRectEqualToRect(platformView.frame, CGRectMake(0, 0, 30, 20)));
   EXPECT_EQ(mutatorView.pathClipViews.count, 1ul);
-  EXPECT_TRUE(
-      CATransform3DEqualToTransform(mutatorView.pathClipViews.firstObject.layer.mask.transform,
-                                    CATransform3DMakeTranslation(-100, -50, 0)));
+  ExpectTransform3DEqual(mutatorView.pathClipViews.firstObject.layer.mask.transform,
+                         CATransform3DMakeTranslation(-100, -50, 0));
 }
 
 TEST(FlutterMutatorViewTest, PathClipViewsAreAddedAndRemoved) {