[wasm] Be more lenient on the names section.

test/mjsunit/wasm/wasm-module-builder.js

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Used for encoding f32 and double constants to bits.
 let __buffer = new ArrayBuffer(8);
 let byte_view = new Int8Array(__buffer);
 let f32_view = new Float32Array(__buffer);
 let f64_view = new Float64Array(__buffer);
 
@@ skipping 504 matching lines @@
     for (let exp of wasm.explicit) {
       if (debug) print("emitting explicit @ " + binary.length);
       binary.emit_bytes(exp);
     }
 
     // Add function names.
     if (has_names) {
       if (debug) print("emitting names @ " + binary.length);
       binary.emit_section(kUnknownSectionCode, section => {
         section.emit_string("name");
-        section.emit_u32v(wasm.functions.length);
+        var count = wasm.functions.length + wasm.num_imported_funcs;
+        section.emit_u32v(count);
+        for (var i = 0; i < wasm.num_imported_funcs; i++) {
+          section.emit_u8(0); // empty string
+          section.emit_u8(0); // local names count == 0
+        }
         for (let func of wasm.functions) {
           var name = func.name == undefined ? "" : func.name;
           section.emit_string(name);
           section.emit_u8(0);  // local names count == 0
         }
       });
     }
 
     return binary;
   }
 
   toBuffer(debug = false) {
     let bytes = this.toArray(debug);
     let buffer = new ArrayBuffer(bytes.length);
     let view = new Uint8Array(buffer);
     for (let i = 0; i < bytes.length; i++) {
       let val = bytes[i];
       if ((typeof val) == "string") val = val.charCodeAt(0);
       view[i] = val | 0;
     }
     return buffer;
   }
 
   instantiate(...args) {
     let module = new WebAssembly.Module(this.toBuffer());
     let instance = new WebAssembly.Instance(module, ...args);
     return instance;
   }
 }