[Extensions] Fix calls to parent SetUp functions in test classes.

This CL fixes one more instance of this issue by moving the code to
the constructor.

Bug: 1117287
Change-Id: I21c1749d1bc037c7952ef7130934c50d37f6b5cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2376044Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: David Bertoni <dbertoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801788}

chrome/browser/extensions/execute_script_apitest.cc

@@ -31,10 +31,7 @@ class ExecuteScriptApiTestBase : public ExtensionApiTest {
 class ExecuteScriptApiTest : public ExecuteScriptApiTestBase,
                              public testing::WithParamInterface<ContextType> {
  protected:
-  void SetUp() override {
-    ExecuteScriptApiTestBase::SetUp();
-    // Service Workers are currently only available on certain channels, so set
-    // the channel for those tests.
+  ExecuteScriptApiTest() {
     if (GetParam() == ContextType::kServiceWorker)
       current_channel_ = std::make_unique<ScopedWorkerBasedExtensionsChannel>();
   }