Fix mock expectation in SubresourceFilterComponentInstallerTest.

This cleans up the output for SubresourceFilterComponentInstallerTest.TestComponentRegistrationWhenFeatureEnabled

[ RUN      ] SubresourceFilterComponentInstallerTest.TestComponentRegistrationWhenFeatureEnabled
[128216:55036:0407/120537.046:3889874656:ERROR:default_component_installer.cc(363)] Component registration failed for Subresource Filter Rules

Review-Url: https://codereview.chromium.org/2803983004
Cr-Commit-Position: refs/heads/master@{#462992}

chrome/browser/component_updater/subresource_filter_component_installer_unittest.cc

@@ -211,7 +211,9 @@ TEST_F(SubresourceFilterComponentInstallerTest,
                             subresource_filter::kActivationScopeNoSites);
   std::unique_ptr<SubresourceFilterMockComponentUpdateService>
       component_updater(new SubresourceFilterMockComponentUpdateService());
-  EXPECT_CALL(*component_updater, RegisterComponent(testing::_)).Times(1);
+  EXPECT_CALL(*component_updater, RegisterComponent(testing::_))
+      .Times(1)
+      .WillOnce(testing::Return(true));
   RegisterSubresourceFilterComponent(component_updater.get());
   base::RunLoop().RunUntilIdle();
 }