Add a sample that uses the JS API to create wasm

This updates 'hello-world.cc' sample.

Change-Id: Id1f3fd222ddd89946e3ab50a8eff5c6477d1f665
Reviewed-on: https://chromium-review.googlesource.com/1089816
Commit-Queue: Ben Smith <binji@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53597}

samples/hello-world.cc

@@ -34,22 +34,63 @@ int main(int argc, char* argv[]) {
     // Enter the context for compiling and running the hello world script.
     v8::Context::Scope context_scope(context);
 
-    // Create a string containing the JavaScript source code.
-    v8::Local<v8::String> source =
-        v8::String::NewFromUtf8(isolate, "'Hello' + ', World!'",
-                                v8::NewStringType::kNormal)
-            .ToLocalChecked();
-
-    // Compile the source code.
-    v8::Local<v8::Script> script =
-        v8::Script::Compile(context, source).ToLocalChecked();
-
-    // Run the script to get the result.
-    v8::Local<v8::Value> result = script->Run(context).ToLocalChecked();
-
-    // Convert the result to an UTF8 string and print it.
-    v8::String::Utf8Value utf8(isolate, result);
-    printf("%s\n", *utf8);
+    {
+      // Create a string containing the JavaScript source code.
+      v8::Local<v8::String> source =
+          v8::String::NewFromUtf8(isolate, "'Hello' + ', World!'",
+                                  v8::NewStringType::kNormal)
+              .ToLocalChecked();
+
+      // Compile the source code.
+      v8::Local<v8::Script> script =
+          v8::Script::Compile(context, source).ToLocalChecked();
+
+      // Run the script to get the result.
+      v8::Local<v8::Value> result = script->Run(context).ToLocalChecked();
+
+      // Convert the result to an UTF8 string and print it.
+      v8::String::Utf8Value utf8(isolate, result);
+      printf("%s\n", *utf8);
+    }
+
+    {
+      // Use the JavaScript API to generate a WebAssembly module.
+      //
+      // |bytes| contains the binary format for the following module:
+      //
+      //     (func (export "add") (param i32 i32) (result i32)
+      //       get_local 0
+      //       get_local 1
+      //       i32.add)
+      //
+      const char* csource = R"(
+        let bytes = new Uint8Array([
+          0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x07, 0x01,
+          0x60, 0x02, 0x7f, 0x7f, 0x01, 0x7f, 0x03, 0x02, 0x01, 0x00, 0x07,
+          0x07, 0x01, 0x03, 0x61, 0x64, 0x64, 0x00, 0x00, 0x0a, 0x09, 0x01,
+          0x07, 0x00, 0x20, 0x00, 0x20, 0x01, 0x6a, 0x0b
+        ]);
+        let module = new WebAssembly.Module(bytes);
+        let instance = new WebAssembly.Instance(module);
+        instance.exports.add(3, 4);
+      )";
+
+      // Create a string containing the JavaScript source code.
+      v8::Local<v8::String> source =
+          v8::String::NewFromUtf8(isolate, csource, v8::NewStringType::kNormal)
+              .ToLocalChecked();
+
+      // Compile the source code.
+      v8::Local<v8::Script> script =
+          v8::Script::Compile(context, source).ToLocalChecked();
+
+      // Run the script to get the result.
+      v8::Local<v8::Value> result = script->Run(context).ToLocalChecked();
+
+      // Convert the result to a uint32 and print it.
+      uint32_t number = result->Uint32Value(context).ToChecked();
+      printf("3 + 4 = %u\n", number);
+    }
   }
 
   // Dispose the isolate and tear down V8.