Add limitation that LoadNexeAndStart must be called on the main thread.

ppapi/native_client/src/trusted/plugin/service_runtime.cc

Index: ppapi/native_client/src/trusted/plugin/service_runtime.cc
diff --git a/ppapi/native_client/src/trusted/plugin/service_runtime.cc b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
index 272bbabebcb18fa79ea7e9bc49e3b084cef88410..ed4fbe8fa363deead3ed157ae5578b7b3bb089a3 100644
--- a/ppapi/native_client/src/trusted/plugin/service_runtime.cc
+++ b/ppapi/native_client/src/trusted/plugin/service_runtime.cc
@@ -418,6 +418,8 @@ void PluginReverseInterface::ReportCrash() {
   if (crash_cb_.pp_completion_callback().func != NULL) {
     NaClLog(4, "PluginReverseInterface::ReportCrash: invoking CB\n");
     pp::Module::Get()->core()->CallOnMainThread(0, crash_cb_, PP_OK);
+    // Clear the callback to avoid it gets invoked twice.
+    crash_cb_ = pp::CompletionCallback();
   } else {
     NaClLog(1,
             "PluginReverseInterface::ReportCrash:"
@@ -683,8 +685,7 @@ void ServiceRuntime::SignalNexeStarted() {
 }
 
 void ServiceRuntime::LoadNexeAndStart(PP_NaClFileInfo file_info,
-                                      const pp::CompletionCallback& started_cb,
-                                      const pp::CompletionCallback& crash_cb) {
+                                      const pp::CompletionCallback& callback) {
   NaClLog(4, "ServiceRuntime::LoadNexeAndStart (handle_valid=%d "
              "token_lo=%" NACL_PRIu64 " token_hi=%" NACL_PRIu64 ")\n",
       file_info.handle != PP_kInvalidFileHandle,
@@ -695,7 +696,9 @@ void ServiceRuntime::LoadNexeAndStart(PP_NaClFileInfo file_info,
             InitReverseService() &&
             LoadModule(file_info) &&
             StartModule();
-  if (!ok) {
+  if (ok) {
+    NaClLog(4, "ServiceRuntime::LoadNexeAndStart (return 1)\n");
+  } else {
     // On a load failure the service runtime does not crash itself to
     // avoid a race where the no-more-senders error on the reverse
     // channel esrvice thread might cause the crash-detection logic to
@@ -707,17 +710,16 @@ void ServiceRuntime::LoadNexeAndStart(PP_NaClFileInfo file_info,
     if (NULL == reverse_service_) {
       // No crash detector thread.
       NaClLog(LOG_ERROR, "scheduling to get crash log\n");
-      pp::Module::Get()->core()->CallOnMainThread(0, crash_cb, PP_OK);
+      // Invoking rev_interface's method is workaround to avoid crash_cb
+      // gets called twice or more. We should clean this up later.
+      rev_interface_->ReportCrash();
       NaClLog(LOG_ERROR, "should fire soon\n");
     } else {
       NaClLog(LOG_ERROR, "Reverse service thread will pick up crash log\n");
     }
-    pp::Module::Get()->core()->CallOnMainThread(0, started_cb, PP_ERROR_FAILED);
-    return;
   }
-
-  NaClLog(4, "ServiceRuntime::LoadNexeAndStart (return 1)\n");
-  pp::Module::Get()->core()->CallOnMainThread(0, started_cb, PP_OK);
+  pp::Module::Get()->core()->CallOnMainThread(
+      0, callback, ok ? PP_OK : PP_ERROR_FAILED);
 }
 
 SrpcClient* ServiceRuntime::SetupAppChannel() {