[wasm] Remove incorrect assembler check.

BUG=chromium:644670
R=ahaas@chromium.org, titzer@chromium.org

Review-Url: https://chromiumcodereview.appspot.com/2438593003
Cr-Commit-Position: refs/heads/master@{#40451}

src/assembler.cc

@@ -351,7 +351,6 @@ void RelocInfo::update_wasm_memory_reference(
                                            icache_flush_mode);
   } else if (IsWasmMemorySizeReference(rmode_)) {
     uint32_t current_size_reference = wasm_memory_size_reference();
-    DCHECK(old_size == 0 || current_size_reference <= old_size);
     uint32_t updated_size_reference =
         new_size + (current_size_reference - old_size);
     unchecked_update_wasm_memory_size(updated_size_reference,

test/mjsunit/wasm/grow-memory.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --expose-wasm --expose-gc --stress-compaction
+// Flags: --expose-wasm --stress-compaction
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
@@ -441,3 +441,20 @@ function testGrowMemoryOutOfBoundsOffset() {
 }
 
 testGrowMemoryOutOfBoundsOffset();
+
+function testGrowMemoryOutOfBoundsOffset2() {
+  var builder = new WasmModuleBuilder();
+  builder.addMemory(16, 128, false);
+  builder.addFunction("main", kSig_v_v)
+      .addBody([
+          kExprI32Const, 20,
+          kExprI32Const, 29,
+          kExprGrowMemory,
+          kExprI32StoreMem, 0, 0xFF, 0xFF, 0xFF, 0x3a
+          ])
+      .exportAs("main");
+  var module = builder.instantiate();
+  assertTraps(kTrapMemOutOfBounds, module.exports.main);
+}
+
+testGrowMemoryOutOfBoundsOffset2();