[wasm-hints] Fix Decoding Bug

When compilation hints are disabled (they are by default) the decoder
failed on custom sections with the name 'compilationHints'. This is
fixed and a test is added.

Bug: v8:9003
Change-Id: I5d25c019a702a722d8baf497d1bcd3a578a2d4bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1557150
Commit-Queue: Frederik Gossen <frgossen@google.com>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60696}

src/wasm/module-decoder.cc

@@ -458,6 +458,7 @@ class ModuleDecoderImpl : public Decoder {
         } else {
           // Ignore this section when feature was disabled. It is an optional
           // custom section anyways.
+          consume_bytes(static_cast<uint32_t>(end_ - start_), nullptr);
         }
         break;
       case kDataCountSectionCode:

test/mjsunit/wasm/compilation-hints-ignored.js

+// Copyright 2019 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.
+
+load('test/mjsunit/wasm/wasm-module-builder.js');
+
+(function testIgnoreCompilationHintsSectionUnlessEnabled() {
+  print(arguments.callee.name);
+  let builder = new WasmModuleBuilder();
+  builder.addImport('mod', 'pow', kSig_i_ii);
+  builder.addFunction('upow', kSig_i_i)
+         .addBody([kExprGetLocal, 0,
+                   kExprGetLocal, 0,
+                   kExprCallFunction, 0])
+         .giveCompilationHint(kCompilationHintStrategyDefault,
+                              kCompilationHintTierInterpreter,
+                              kCompilationHintTierInterpreter)
+         .exportFunc();
+  let instance = builder.instantiate({mod: {pow: Math.pow}});
+  assertEquals(27, instance.exports.upow(3))
+})();