Report PPAPI plugin load error code to UMA.

base/native_library_posix.cc

Index: base/native_library_posix.cc
diff --git a/base/native_library_posix.cc b/base/native_library_posix.cc
index dfa20fc01cf78ef6ab2061f3eefb32d3c8f324c0..3179a93833c0ad20beafe800d8e24d3a21d127b5 100644
--- a/base/native_library_posix.cc
+++ b/base/native_library_posix.cc
@@ -13,9 +13,13 @@
 
 namespace base {
 
+std::string NativeLibraryLoadError::ToString() const {
+  return message;
+}
+
 // static
 NativeLibrary LoadNativeLibrary(const FilePath& library_path,
-                                std::string* error) {
+                                NativeLibraryLoadError* error) {
   // dlopen() opens the file off disk.
   base::ThreadRestrictions::AssertIOAllowed();
 
@@ -25,7 +29,7 @@ NativeLibrary LoadNativeLibrary(const FilePath& library_path,
   // and http://crbug.com/40794.
   void* dl = dlopen(library_path.value().c_str(), RTLD_LAZY);
   if (!dl && error)
-    *error = dlerror();
+    error->message = dlerror();
 
   return dl;
 }