[wasm] Mutable globals cannot be imported

This fixes another spec tests.

R=rossberg@chromium.org, titzer@chromium.org
TEST=WasmModuleVerifyTest.ImportTable_mutable_global

Review-Url: https://codereview.chromium.org/2484803002
Cr-Commit-Position: refs/heads/master@{#40831}

src/wasm/module-decoder.cc

@@ -337,6 +337,9 @@ class ModuleDecoder : public Decoder {
             WasmGlobal* global = &module->globals.back();
             global->type = consume_value_type();
             global->mutability = consume_u8("mutability") != 0;
+            if (global->mutability) {
+              error("mutable globals cannot be imported");
+            }
             break;
           }
           default:

test/unittests/wasm/module-decoder-unittest.cc

@@ -894,6 +894,37 @@ TEST_F(WasmModuleVerifyTest, ImportTable_nosigs1) {
   EXPECT_VERIFIES(data);
 }
 
+TEST_F(WasmModuleVerifyTest, ImportTable_mutable_global) {
+  {
+    static const byte data[] = {
+        SECTION(Import, 8),  // section header
+        1,                   // number of imports
+        NAME_LENGTH(1),      // --
+        'm',                 // module name
+        NAME_LENGTH(1),      // --
+        'f',                 // global name
+        kExternalGlobal,     // import kind
+        kLocalI32,           // type
+        0,                   // mutability
+    };
+    EXPECT_VERIFIES(data);
+  }
+  {
+    static const byte data[] = {
+        SECTION(Import, 8),  // section header
+        1,                   // sig table
+        NAME_LENGTH(1),      // --
+        'm',                 // module name
+        NAME_LENGTH(1),      // --
+        'f',                 // global name
+        kExternalGlobal,     // import kind
+        kLocalI32,           // type
+        1,                   // mutability
+    };
+    EXPECT_FAILURE(data);
+  }
+}
+
 TEST_F(WasmModuleVerifyTest, ImportTable_nosigs2) {
   static const byte data[] = {
       SECTION(Import, 6),  1,    // sig table