Remove int.pow and double.pow from VM library.

runtime/lib/math.cc

Index: runtime/lib/math.cc
diff --git a/runtime/lib/math.cc b/runtime/lib/math.cc
index 317045dce5b1cf1c278e06a7c862a619f995f803..ca7c7e6da90d04f2ee8a60443505c68ec697b3c5 100644
--- a/runtime/lib/math.cc
+++ b/runtime/lib/math.cc
@@ -66,6 +66,15 @@ DEFINE_NATIVE_ENTRY(Math_log, 1) {
   return Double::New(log(operand.value()));
 }
 
+DEFINE_NATIVE_ENTRY(Math_doublePow, 2) {
+  const double operand =
+      Double::CheckedHandle(arguments->NativeArgAt(0)).value();
+  GET_NON_NULL_NATIVE_ARGUMENT(
+      Double, exponent_object, arguments->NativeArgAt(1));
+  const double exponent = exponent_object.value();
+  return Double::New(pow(operand, exponent));
+}
+
 
 // Returns the typed-data array store in '_Random._state' field.
 static RawTypedData* GetRandomStateArray(const Instance& receiver) {