linux: don't always print dlopen errors from LoadNativeLibrary

base/native_library.h

Index: base/native_library.h
diff --git a/base/native_library.h b/base/native_library.h
index 9809c987c864f3a82dc96e881f18241000300694..289616344b41527f606cfefbbfa1716d73938ec6 100644
--- a/base/native_library.h
+++ b/base/native_library.h
@@ -52,8 +52,11 @@ typedef void* NativeLibrary;
 #endif  // OS_*
 
 // Loads a native library from disk.  Release it with UnloadNativeLibrary when
-// you're done.
-BASE_API NativeLibrary LoadNativeLibrary(const FilePath& library_path);
+// you're done.  Returns NULL on failure.
+// If |err| is not NULL, it may be filled in with an error message on
+// error.
+BASE_API NativeLibrary LoadNativeLibrary(const FilePath& library_path,
+                                         std::string* error);
 
 #if defined(OS_WIN)
 // Loads a native library from disk.  Release it with UnloadNativeLibrary when