cppgc: Fix compilation error on gcc 8

The following error is currently thrown on gcc 8:

error: suggest explicit braces to avoid ambiguous 'else'

Change-Id: I1498ef3f6f58874488a4e6897f488c122f4a7f76
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2550841Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/master@{#71292}

test/unittests/heap/cppgc/stats-collector-scopes-unittest.cc

@@ -24,7 +24,9 @@ class DelegatingTracingControllerImpl : public TracingController {
     static char phases[2] = {'B', 'E'};
     EXPECT_EQ(phases[AddTraceEvent_callcount], phase);
     EXPECT_TRUE(*category_enabled_flag);
-    if (expected_name) EXPECT_EQ(0, strcmp(expected_name, name));
+    if (expected_name) {
+      EXPECT_EQ(0, strcmp(expected_name, name));
+    }
     stored_num_args += num_args;
     for (int i = 0; i < num_args; ++i) {
       stored_arg_names.push_back(arg_names[i]);