[wasm] Local decl parsing tweak.

R=ahaas@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1860103002

Cr-Commit-Position: refs/heads/master@{#35286}

src/wasm/ast-decoder.cc

@@ -416,7 +416,6 @@ class SR_WasmDecoder : public WasmDecoder {
     DecodeLocalDecls();
     if (failed()) return false;
     decls.decls_encoded_size = pc_offset();
-    decls.total_local_count = 0;
     decls.local_types.reserve(local_type_vec_.size());
     for (size_t pos = 0; pos < local_type_vec_.size();) {
       uint32_t count = 0;
@@ -425,9 +424,9 @@ class SR_WasmDecoder : public WasmDecoder {
         pos++;
         count++;
       }
-      decls.total_local_count += count;
       decls.local_types.push_back(std::pair<LocalType, uint32_t>(type, count));
     }
+    decls.total_local_count = static_cast<uint32_t>(local_type_vec_.size());
     return true;
   }
 

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

@@ -2246,7 +2246,7 @@ TEST_F(LocalDeclDecoderTest, OneLocal) {
 
     LocalTypeMap map = Expand(decls);
     EXPECT_EQ(1, map.size());
-    EXPECT_EQ(type, map.at(0));
+    EXPECT_EQ(type, map[0]);
   }
 }