Add the UtilityProcessMojoClient class and convert SafeJsonParser

components/safe_json/safe_json_parser_impl.cc

Index: components/safe_json/safe_json_parser_impl.cc
diff --git a/components/safe_json/safe_json_parser_impl.cc b/components/safe_json/safe_json_parser_impl.cc
index 40edbc7e112a1a27d6bf6aaf408f2a8f5069d837..09909e13045c3c785302276bcb26d5933b6eb237 100644
--- a/components/safe_json/safe_json_parser_impl.cc
+++ b/components/safe_json/safe_json_parser_impl.cc
@@ -4,23 +4,14 @@
 
 #include "components/safe_json/safe_json_parser_impl.h"
 
-#include <utility>
-
+#include "base/callback.h"
 #include "base/sequenced_task_runner.h"
-#include "base/strings/utf_string_conversions.h"
 #include "base/threading/sequenced_task_runner_handle.h"
-#include "base/threading/thread_task_runner_handle.h"
-#include "base/tuple.h"
 #include "base/values.h"
 #include "content/public/browser/browser_thread.h"
-#include "content/public/browser/utility_process_host.h"
-#include "content/public/common/service_registry.h"
 #include "grit/components_strings.h"
 #include "ui/base/l10n/l10n_util.h"
 
-using content::BrowserThread;
-using content::UtilityProcessHost;
-
 namespace safe_json {
 
 SafeJsonParserImpl::SafeJsonParserImpl(const std::string& unsafe_json,
@@ -32,90 +23,81 @@ SafeJsonParserImpl::SafeJsonParserImpl(const std::string& unsafe_json,
   io_thread_checker_.DetachFromThread();
 }
 
-SafeJsonParserImpl::~SafeJsonParserImpl() {
+SafeJsonParserImpl::~SafeJsonParserImpl() = default;
+
+void SafeJsonParserImpl::Start() {
+  caller_task_runner_ = base::SequencedTaskRunnerHandle::Get();
+
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO, FROM_HERE,
+      base::Bind(&SafeJsonParserImpl::StartOnIOThread, base::Unretained(this)));
 }
 
-void SafeJsonParserImpl::StartWorkOnIOThread() {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+void SafeJsonParserImpl::StartOnIOThread() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   DCHECK(io_thread_checker_.CalledOnValidThread());
-  // TODO(amistry): This UtilityProcessHost dance is likely to be done multiple
-  // times as more tasks are migrated to Mojo. Create some sort of helper class
-  // to eliminate the code duplication.
-  utility_process_host_ = UtilityProcessHost::Create(
-      this, base::ThreadTaskRunnerHandle::Get().get())->AsWeakPtr();
-  utility_process_host_->SetName(
-      l10n_util::GetStringUTF16(IDS_UTILITY_PROCESS_JSON_PARSER_NAME));
-  if (!utility_process_host_->Start()) {
-    ReportResults();
-    return;
-  }
+  mojo_json_parser_.reset(
+      new content::UtilityProcessMojoClient<mojom::SafeJsonParser>(
+          l10n_util::GetStringUTF16(IDS_UTILITY_PROCESS_JSON_PARSER_NAME),
+          base::Bind(&SafeJsonParserImpl::OnConnectionError,
+                     base::Unretained(this))));
 
-  content::ServiceRegistry* service_registry =
-      utility_process_host_->GetServiceRegistry();
-  service_registry->ConnectToRemoteService(mojo::GetProxy(&service_));
-  service_.set_connection_error_handler(
-      base::Bind(&SafeJsonParserImpl::ReportResults, this));
+  mojo_json_parser_->Start();
 
-  service_->Parse(unsafe_json_,
-                  base::Bind(&SafeJsonParserImpl::OnParseDone, this));
+  mojo_json_parser_->service()->Parse(
+      std::move(unsafe_json_),
+      base::Bind(&SafeJsonParserImpl::OnParseDone, base::Unretained(this)));
 }
 
-void SafeJsonParserImpl::ReportResults() {
-  // There should be a DCHECK_CURRENTLY_ON(BrowserThread::IO) here. However, if
-  // the parser process is still alive on shutdown, this might run on the IO
-  // thread while the IO thread message loop is shutting down. This happens
-  // after the IO thread has unregistered from the BrowserThread list, causing
-  // the DCHECK to fail.
+void SafeJsonParserImpl::OnConnectionError() {
   DCHECK(io_thread_checker_.CalledOnValidThread());
-  io_thread_checker_.DetachFromThread();
 
-  // Maintain a reference to |this| since either |utility_process_host_| or
-  // |service_| may have the last reference and destroying those might delete
-  // |this|.
-  scoped_refptr<SafeJsonParserImpl> ref(this);
-  // Shut down the utility process if it's still running.
-  delete utility_process_host_.get();
-  service_.reset();
+  // Shut down the utility process.
+  mojo_json_parser_.reset();
 
   caller_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&SafeJsonParserImpl::ReportResultsOnOriginThread, this));
-}
-
-void SafeJsonParserImpl::ReportResultsOnOriginThread() {
-  DCHECK(caller_task_runner_->RunsTasksOnCurrentThread());
-  if (error_.empty() && parsed_json_) {
-    if (!success_callback_.is_null())
-      success_callback_.Run(std::move(parsed_json_));
-  } else {
-    if (!error_callback_.is_null())
-      error_callback_.Run(error_);
-  }
-}
-
-bool SafeJsonParserImpl::OnMessageReceived(const IPC::Message& message) {
-  return false;
+      FROM_HERE, base::Bind(&SafeJsonParserImpl::ReportResults,
+                            base::Unretained(this), nullptr, "Json error"));
 }
 
 void SafeJsonParserImpl::OnParseDone(const base::ListValue& wrapper,
-                                     mojo::String error) {
+                                     const mojo::String& error) {
   DCHECK(io_thread_checker_.CalledOnValidThread());
+
+  // Shut down the utility process.
+  mojo_json_parser_.reset();
+
+  std::unique_ptr<base::Value> parsed_json;
+  std::string error_message;
   if (!wrapper.empty()) {
-    const base::Value* value = NULL;
+    const base::Value* value = nullptr;
     CHECK(wrapper.Get(0, &value));
-    parsed_json_.reset(value->DeepCopy());
+    parsed_json.reset(value->DeepCopy());
   } else {
-    error_ = error.get();
+    error_message = error.get();
   }
-  ReportResults();
+
+  // Call ReportResults() on caller's thread.
+  caller_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&SafeJsonParserImpl::ReportResults, base::Unretained(this),
+                 base::Passed(&parsed_json), error_message));
 }
 
-void SafeJsonParserImpl::Start() {
-  caller_task_runner_ = base::SequencedTaskRunnerHandle::Get();
+void SafeJsonParserImpl::ReportResults(std::unique_ptr<base::Value> parsed_json,
+                                       const std::string& error) {
+  DCHECK(caller_task_runner_->RunsTasksOnCurrentThread());
+  if (error.empty() && parsed_json) {
+    if (!success_callback_.is_null())
+      success_callback_.Run(std::move(parsed_json));
+  } else {
+    if (!error_callback_.is_null())
+      error_callback_.Run(error);
+  }
 
-  BrowserThread::PostTask(
-      BrowserThread::IO, FROM_HERE,
-      base::Bind(&SafeJsonParserImpl::StartWorkOnIOThread, this));
+  // The parsing is done whether an error occured or not, so this instance can
+  // be cleaned up.
+  delete this;
 }
 
 }  // namespace safe_json