[wasm] Support importing constructed {WebAssmebly.Function}.

This adds support for properly importing {WebAssembly.Function} objects
that were constructed in JavaScript and just wrap a JavaScript callable.

R=ahaas@chromium.org
TEST=mjsunit/wasm/type-reflection
BUG=v8:7742

Change-Id: I00e01db0d85b83d405eb28517d00fba62c253985
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1690949
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62641}

src/compiler/wasm-compiler.cc

@@ -6015,8 +6015,9 @@ std::pair<WasmImportCallKind, Handle<JSReceiver>> ResolveWasmImportCall(
     if (!js_function->MatchesSignature(expected_sig)) {
       return std::make_pair(WasmImportCallKind::kLinkError, callable);
     }
-    // TODO(7742): Implement proper handling of this case.
-    UNIMPLEMENTED();
+    Isolate* isolate = callable->GetIsolate();
+    // Resolve the short-cut to the underlying callable and continue.
+    callable = handle(js_function->GetCallable(), isolate);
   }
   if (WasmCapiFunction::IsWasmCapiFunction(*callable)) {
     auto capi_function = Handle<WasmCapiFunction>::cast(callable);

test/mjsunit/wasm/type-reflection.js

@@ -319,8 +319,7 @@ load('test/mjsunit/wasm/wasm-module-builder.js');
     /wasm function signature contains illegal type/);
 })();
 
-// TODO(7742): Enable once imported constructed functions are callable.
-/*(function TestFunctionModuleImportMatchingSig() {
+(function TestFunctionModuleImportMatchingSig() {
   let builder = new WasmModuleBuilder();
   let fun = new WebAssembly.Function({parameters:[], results:["i32"]}, _ => 7);
   let fun_index = builder.addImport("m", "fun", kSig_i_v)
@@ -331,7 +330,7 @@ load('test/mjsunit/wasm/wasm-module-builder.js');
       .exportFunc();
   let instance = builder.instantiate({ m: { fun: fun }});
   assertEquals(7, instance.exports.main());
-})();*/
+})();
 
 (function TestFunctionModuleImportMismatchingSig() {
   let builder = new WasmModuleBuilder();