Report PPAPI plugin load error code to UMA.

base/native_library.h

Index: base/native_library.h
diff --git a/base/native_library.h b/base/native_library.h
index d7513d0b050e181b4df913e276b39051aef5318f..0d864159f327c01c2591615f736d77e249e34cc7 100644
--- a/base/native_library.h
+++ b/base/native_library.h
@@ -52,9 +52,12 @@ typedef void* NativeLibrary;
 
 // Loads a native library from disk.  Release it with UnloadNativeLibrary when
 // you're done.  Returns NULL on failure.
-// If |error| is not NULL, it may be filled in with an error message on error.
+// If |error_message| or |error_code| is not NULL, they may be filled in with
+// an error message or an error code, respectively, on load error if the
+// platform supports it.
 BASE_EXPORT NativeLibrary LoadNativeLibrary(const FilePath& library_path,
-                                            std::string* error);
+                                            std::string* error_message,
+                                            uint32* error_code = NULL);
 
 #if defined(OS_WIN)
 // Loads a native library from disk.  Release it with UnloadNativeLibrary when