Report PPAPI plugin load error code to UMA.

mojo/shell/in_process_dynamic_service_runner.cc

Index: mojo/shell/in_process_dynamic_service_runner.cc
diff --git a/mojo/shell/in_process_dynamic_service_runner.cc b/mojo/shell/in_process_dynamic_service_runner.cc
index e3661586a5003903bfe4427fa55b65f4c99cd1d5..3d63dee2195b5581e9b4a2197c2c57ac0634ca0e 100644
--- a/mojo/shell/in_process_dynamic_service_runner.cc
+++ b/mojo/shell/in_process_dynamic_service_runner.cc
@@ -49,11 +49,11 @@ void InProcessDynamicServiceRunner::Run() {
       base::Bind(base::IgnoreResult(&base::DeleteFile), app_path_, false));
 
   do {
-    std::string load_error;
+    base::NativeLibraryLoadError error;
     base::ScopedNativeLibrary app_library(
-        base::LoadNativeLibrary(app_path_, &load_error));
+        base::LoadNativeLibrary(app_path_, &error));
     if (!app_library.is_valid()) {
-      LOG(ERROR) << "Failed to load library (error: " << load_error << ")";
+      LOG(ERROR) << "Failed to load library (error: " << error << ")";
       break;
     }