Add unit tests for ExtensionInstallEventLogUploader

ExtensionInstallEventLogUploader class acts as an adapter between the
system that captures and stores extension install event logs and the
policy system which uploads them to the management server. Add unit
tests for the class.

Bug: 1100862
Change-Id: Id0e753ebe846ce25417e8ce6be8159007b9335f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2275894Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Swapnil Gupta <swapnilgupta@google.com>
Cr-Commit-Position: refs/heads/master@{#784478}

chrome/browser/chromeos/BUILD.gn

@@ -3261,6 +3261,7 @@ source_set("unit_tests") {
     "policy/extension_cache_unittest.cc",
     "policy/extension_install_event_log_collector_unittest.cc",
     "policy/extension_install_event_log_unittest.cc",
+    "policy/extension_install_event_log_uploader_unittest.cc",
     "policy/extension_install_event_logger_unittest.cc",
     "policy/external_data_handlers/device_native_printers_external_data_handler_unittest.cc",
     "policy/fake_affiliated_invalidation_service_provider.cc",

components/policy/core/common/cloud/mock_cloud_policy_client.h

@@ -67,6 +67,7 @@ class MockCloudPolicyClient : public CloudPolicyClient {
                     const enterprise_management::ChildStatusReportRequest*,
                     StatusCallback&));
   MOCK_METHOD0(CancelAppInstallReportUpload, void(void));
+  MOCK_METHOD0(CancelExtensionInstallReportUpload, void(void));
   void UpdateGcmId(const std::string& id, StatusCallback callback) override {
     UpdateGcmId_(id, callback);
   }
@@ -109,6 +110,12 @@ class MockCloudPolicyClient : public CloudPolicyClient {
     UploadAppInstallReport_(value, callback);
   }
   MOCK_METHOD2(UploadAppInstallReport_, void(base::Value&, StatusCallback&));
+  void UploadExtensionInstallReport(base::Value value,
+                                    StatusCallback callback) override {
+    UploadExtensionInstallReport_(value, callback);
+  }
+  MOCK_METHOD2(UploadExtensionInstallReport_,
+               void(base::Value&, StatusCallback&));
 
   MOCK_METHOD5(ClientCertProvisioningStartCsr,
                void(const std::string& cert_scope,