refactor!: use BackgroundThreads from common (#1262)

* refactor: use `BackgroundThreads` from `common`

fixes #1250

* update API/ABI after rebase

Author: mr-salty

ci/test-api/spanner_client.expected.abi.dump.gz

@@ -97,7 +97,6 @@ configure_file(version_info.h.in ${CMAKE_CURRENT_SOURCE_DIR}/version_info.h)
 add_library(
     spanner_client
     ${CMAKE_CURRENT_BINARY_DIR}/internal/build_info.cc
-    background_threads.h
     backoff_policy.h
     batch_dml_result.h
     bytes.cc
@@ -126,8 +125,6 @@ add_library(
     instance_admin_connection.h
     internal/api_client_header.cc
     internal/api_client_header.h
-    internal/background_threads_impl.cc
-    internal/background_threads_impl.h
     internal/build_info.h
     internal/compiler_info.cc
     internal/compiler_info.h
@@ -314,7 +311,6 @@ function (spanner_client_define_tests)
         instance_admin_connection_test.cc
         instance_test.cc
         internal/api_client_header_test.cc
-        internal/background_threads_test.cc
         internal/build_info_test.cc
         internal/compiler_info_test.cc
         internal/connection_impl_test.cc

google/cloud/spanner/CMakeLists.txt

@@ -13,8 +13,8 @@
 // limitations under the License.
 
 #include "google/cloud/spanner/connection_options.h"
-#include "google/cloud/spanner/internal/background_threads_impl.h"
 #include "google/cloud/spanner/internal/compiler_info.h"
+#include "google/cloud/internal/background_threads_impl.h"
 #include "google/cloud/internal/getenv.h"
 #include "google/cloud/log.h"
 #include <sstream>
@@ -39,7 +39,7 @@ ConnectionOptions::ConnectionOptions(
       user_agent_prefix_(internal::BaseUserAgentPrefix()),
       background_threads_factory_([] {
         return google::cloud::internal::make_unique<
-            internal::AutomaticallyCreatedBackgroundThreads>();
+            google::cloud::internal::AutomaticallyCreatedBackgroundThreads>();
       }) {
   auto tracing =
       google::cloud::internal::GetEnv("GOOGLE_CLOUD_CPP_ENABLE_TRACING");
@@ -85,7 +85,7 @@ ConnectionOptions& ConnectionOptions::DisableBackgroundThreads(
     google::cloud::grpc_utils::CompletionQueue const& cq) {
   background_threads_factory_ = [cq] {
     return google::cloud::internal::make_unique<
-        internal::CustomerSuppliedBackgroundThreads>(cq);
+        google::cloud::internal::CustomerSuppliedBackgroundThreads>(cq);
   };
   return *this;
 }

google/cloud/spanner/background_threads.h

@@ -15,9 +15,9 @@
 #ifndef GOOGLE_CLOUD_CPP_SPANNER_GOOGLE_CLOUD_SPANNER_CONNECTION_OPTIONS_H
 #define GOOGLE_CLOUD_CPP_SPANNER_GOOGLE_CLOUD_SPANNER_CONNECTION_OPTIONS_H
 
-#include "google/cloud/spanner/background_threads.h"
 #include "google/cloud/spanner/tracing_options.h"
 #include "google/cloud/spanner/version.h"
+#include "google/cloud/background_threads.h"
 #include "google/cloud/grpc_utils/completion_queue.h"
 #include "google/cloud/status_or.h"
 #include <google/spanner/admin/database/v1/spanner_database_admin.grpc.pb.h>

google/cloud/spanner/connection_options.cc

@@ -17,7 +17,6 @@
 """Automatically generated source lists for spanner_client - DO NOT EDIT."""
 
 spanner_client_hdrs = [
-    "background_threads.h",
     "backoff_policy.h",
     "batch_dml_result.h",
     "bytes.h",
@@ -35,7 +34,6 @@ spanner_client_hdrs = [
     "instance_admin_client.h",
     "instance_admin_connection.h",
     "internal/api_client_header.h",
-    "internal/background_threads_impl.h",
     "internal/build_info.h",
     "internal/compiler_info.h",
     "internal/connection_impl.h",
@@ -98,7 +96,6 @@ spanner_client_srcs = [
     "instance_admin_client.cc",
     "instance_admin_connection.cc",
     "internal/api_client_header.cc",
-    "internal/background_threads_impl.cc",
     "internal/compiler_info.cc",
     "internal/connection_impl.cc",
     "internal/database_admin_logging.cc",

google/cloud/spanner/connection_options.h

@@ -27,7 +27,6 @@ spanner_client_unit_tests = [
     "instance_admin_connection_test.cc",
     "instance_test.cc",
     "internal/api_client_header_test.cc",
-    "internal/background_threads_test.cc",
     "internal/build_info_test.cc",
     "internal/compiler_info_test.cc",
     "internal/connection_impl_test.cc",