[dart2wasm] Fix double.pow

Handle these two edge cases documented in `pow`:

- if x is 1.0, the result is always 1.0
- if y is Infinity and x is -1, the result is 1.0

New passing tests:

- co19/LibTest/math/pow_A04_t01
- co19/LibTest/math/pow_A14_t01
- co19/LibTest/math/pow_A16_t01
- lib/math/double_pow_test

Fixes #50505

Change-Id: I42266e9b52edd853133db8aeaafe9d5aa73a1449
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/268960
Reviewed-by: Aske Simon Christensen <askesc@google.com>
Commit-Queue: Ömer Ağacan <omersa@google.com>

sdk/lib/_internal/wasm/lib/math_patch.dart

@@ -63,7 +63,20 @@ num pow(num x, num exponent) {
   if ((x is int) && (exponent is int) && (exponent >= 0)) {
     return _intPow(x, exponent);
   }
-  return _doublePow(x.toDouble(), exponent.toDouble());
+
+  double xDouble = x.toDouble();
+
+  if (xDouble == 1.0) {
+    return 1.0;
+  }
+
+  double exponentDouble = exponent.toDouble();
+
+  if (xDouble == -1.0 && exponent.isInfinite) {
+    return 1.0;
+  }
+
+  return _doublePow(xDouble, exponentDouble);
 }
 
 @pragma("wasm:import", "Math.pow")