Add Float32x4List.fromList to runtime implementation and some tests

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 739eae8bcd88a70eb53e41cc43660953643611cd..f75b4bbbdfd4b49028682e50ca858a90e2444d8d 100644
--- a/sdk/lib/typed_data/typed_data.dart
+++ b/sdk/lib/typed_data/typed_data.dart
@@ -798,6 +798,12 @@ abstract class Float32x4List implements List<Float32x4>, TypedData {
   external factory Float32x4List(int length);
 
   /**
+   * Creates a [Float32x4List] with the same size as the [elements] list
+   * and copies over the elements.
+   */
+  external factory Float32x4List.fromList(List<Float32x4> elements);
+
+  /**
    * Creates a [Float32x4List] _view_ of the specified region in the specified
    * byte buffer. Changes in the [Float32x4List] will be visible in the byte
    * buffer and vice versa. If the [offsetInBytes] index of the region is not