Add simple fake for native service manager.

Reusing the existing binder-based native service manager has
proved problematic in host/test environments.

So as a workaround, this commit creates a IServiceManager native
implementation that can be communicated with directly.

Bug: 147595993
Test: m fakeservicemanager_test; fakeservicemanager_test
Change-Id: Icfa6f2fd314bd5a7b3d5e8a064b487f92b99b133
diff --git a/libs/fakeservicemanager/ServiceManager.cpp b/libs/fakeservicemanager/ServiceManager.cpp
new file mode 100644
index 0000000..6964324
--- /dev/null
+++ b/libs/fakeservicemanager/ServiceManager.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ServiceManager.h"
+
+namespace android {
+
+ServiceManager::ServiceManager() {}
+
+sp<IBinder> ServiceManager::getService( const String16& name) const {
+    // Servicemanager is single-threaded and cannot block. This method exists for legacy reasons.
+    return checkService(name);
+}
+
+sp<IBinder> ServiceManager::checkService( const String16& name) const {
+    auto it = mNameToService.find(name);
+    if (it == mNameToService.end()) {
+        return nullptr;
+    }
+    return it->second;
+}
+
+status_t ServiceManager::addService(const String16& name, const sp<IBinder>& service,
+                                bool /*allowIsolated*/,
+                                int /*dumpsysFlags*/) {
+    mNameToService[name] = service;
+    return NO_ERROR;
+}
+
+Vector<String16> ServiceManager::listServices(int /*dumpsysFlags*/) {
+    Vector<String16> services;
+    for (auto const& [name, service] : mNameToService) {
+        (void) service;
+         services.push_back(name);
+    }
+  return services;
+}
+
+IBinder* ServiceManager::onAsBinder() {
+    return nullptr;
+}
+
+sp<IBinder> ServiceManager::waitForService(const String16& name) {
+    return checkService(name);
+}
+
+bool ServiceManager::isDeclared(const String16& name) {
+    return mNameToService.find(name) != mNameToService.end();
+}
+
+}  // namespace android