Add signMask getter to Float32x4

sdk/lib/typed_data/typed_data.dart

Index: sdk/lib/typed_data/typed_data.dart
diff --git a/sdk/lib/typed_data/typed_data.dart b/sdk/lib/typed_data/typed_data.dart
index 7184e4797769756a0ca6577124faa88fd51101f5..886c86af19741b71cc161423d21a0b5b142ec019 100644
--- a/sdk/lib/typed_data/typed_data.dart
+++ b/sdk/lib/typed_data/typed_data.dart
@@ -876,6 +876,9 @@ abstract class Float32x4 {
   /// Extracted w value.
   double get w;
 
+  /// Extract the sign bits from each lane return them in the first 4 bits.
+  int get signMask;
+
   /// Mask passed to [shuffle].
   static const int XXXX = 0x0;
   static const int XXXY = 0x40;
@@ -1211,6 +1214,9 @@ abstract class Uint32x4 {
   /// Extract 32-bit mask from w lane.
   int get w;
 
+  /// Extract the top bit from each lane return them in the first 4 bits.
+  int get signMask;
+
   /// Returns a new [Uint32x4] copied from [this] with a new x value.
   Uint32x4 withX(int x);
   /// Returns a new [Uint32x4] copied from [this] with a new y value.