Remove unnecessary checks on the existence of fetch. NFC (emscripten-core#23166)

As of emscripten-core#23118 we can assume and browser and worker environments always
include `fetch`.

Author: sbc100

src/preamble.js

@@ -818,10 +818,10 @@ async function instantiateAsync(binary, binaryFile, imports) {
 #if !SINGLE_FILE
   if (!binary &&
       typeof WebAssembly.instantiateStreaming == 'function' &&
-      !isDataURI(binaryFile) &&
+      !isDataURI(binaryFile)
 #if ENVIRONMENT_MAY_BE_WEBVIEW
       // Don't use streaming for file:// delivered objects in a webview, fetch them synchronously.
-      !isFileURI(binaryFile) &&
+      && !isFileURI(binaryFile)
 #endif
 #if ENVIRONMENT_MAY_BE_NODE
       // Avoid instantiateStreaming() on Node.js environment for now, as while
@@ -830,9 +830,13 @@ async function instantiateAsync(binary, binaryFile, imports) {
       //
       // Reference:
       //   https://github.com/emscripten-core/emscripten/pull/16917
-      !ENVIRONMENT_IS_NODE &&
+      && !ENVIRONMENT_IS_NODE
 #endif
-      typeof fetch == 'function') {
+#if ENVIRONMENT_MAY_BE_SHELL
+      // Shell environments don't have fetch.
+      && !ENVIRONMENT_IS_SHELL
+#endif
+     ) {
     try {
       var response = fetch(binaryFile, {{{ makeModuleReceiveExpr('fetchSettings', "{ credentials: 'same-origin' }") }}});
 #if USE_OFFSET_CONVERTER

src/source_map_support.js

@@ -107,7 +107,7 @@ function getSourceMap() {
 }
 
 function getSourceMapPromise() {
-  if ((ENVIRONMENT_IS_WEB || ENVIRONMENT_IS_WORKER) && typeof fetch == 'function') {
+  if (ENVIRONMENT_IS_WEB || ENVIRONMENT_IS_WORKER) {
     return fetch(wasmSourceMapFile, {{{ makeModuleReceiveExpr('fetchSettings', "{ credentials: 'same-origin' }") }}})
       .then((response) => response.json())
       .catch(getSourceMap);

test/other/codesize/test_codesize_cxx_ctors1.gzsize

@@ -1 +1 @@
-8545
+8542

test/other/codesize/test_codesize_cxx_ctors1.jssize

@@ -1 +1 @@
-20951
+20925

test/other/codesize/test_codesize_cxx_ctors2.gzsize

@@ -1 +1 @@
-8530
+8526

test/other/codesize/test_codesize_cxx_ctors2.jssize

@@ -1 +1 @@
-20919
+20893

test/other/codesize/test_codesize_cxx_except.gzsize

@@ -1 +1 @@
-9579
+9572

test/other/codesize/test_codesize_cxx_except.jssize

@@ -1 +1 @@
-24796
+24770

test/other/codesize/test_codesize_cxx_except_wasm.gzsize

@@ -1 +1 @@
-8508
+8503

test/other/codesize/test_codesize_cxx_except_wasm.jssize

@@ -1 +1 @@
-20845
+20819