[fuchsia] Fix ThemeManagerTest suite.

The test suite was removing all services from the browser process'
incoming service directory, causing the NetworkService to sometimes
fail to be able to contact the platform network stack.

Fix the test suite not to disable access to platform services.

Bug: 1150754
Change-Id: Idd34735bcd494502af9391ab212313cea2b94c22
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2637517
Commit-Queue: Wez <wez@chromium.org>
Commit-Queue: Marina Ciocea <marinaciocea@chromium.org>
Auto-Submit: Wez <wez@chromium.org>
Reviewed-by: Marina Ciocea <marinaciocea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844814}

fuchsia/engine/browser/theme_manager_browsertest.cc

@@ -37,12 +37,13 @@ class ThemeManagerTest : public cr_fuchsia::WebEngineBrowserTest,
 
  protected:
   void SetUpOnMainThread() override {
+    component_context_.emplace(
+        base::TestComponentContextForProcess::InitialState::kCloneAll);
+    display_binding_.emplace(component_context_->additional_services(), this);
+
     ASSERT_TRUE(embedded_test_server()->Start());
     cr_fuchsia::WebEngineBrowserTest::SetUpOnMainThread();
 
-    component_context_.emplace(
-        base::TestComponentContextForProcess::InitialState::kEmpty);
-    display_binding_.emplace(component_context_->additional_services(), this);
     frame_ = WebEngineBrowserTest::CreateFrame(&navigation_listener_);
     base::RunLoop().RunUntilIdle();
     frame_->GetNavigationController(controller_.NewRequest());