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..564234ae11dc0d3daa04f918a8a5d700bb4d751d 100644
--- a/base/native_library.h
+++ b/base/native_library.h
@@ -50,11 +50,18 @@ typedef NativeLibraryStruct* NativeLibrary;
 typedef void* NativeLibrary;
 #endif  // OS_*
 
+#if defined(OS_WIN)
+typedef DWORD NativeLibraryLoadError;

[ddorwin, 2014/03/21 20:06:32]

While more explicit about what to expect, this forces the caller to ifdef its
code.
On the other hand, this is most often used for LOG statements, which happily
cast and work fine.

It seems like an odd thing to expose to all of Chromium (it's in base/). Also,
there is the issue of initialization. To address that, this could be a class
with a operator().

[xhwang, 2014/03/21 22:33:28]

I fixed the initialization issue with a struct. Most callers don't need to care
about ifdef. ppapi_thread.cc is the only exception because UMA doesn't support
string very well.

+#else
+typedef std::string NativeLibraryLoadError;
+#endif  // OS_WIN
+
 // 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| is not NULL, it may be filled in on load error if the platform

[ddorwin, 2014/03/21 20:06:32]

I think we can drop the "if the platform..." part. Maybe we can replace "may"
with "can" when the Mac implementation is fixed.

[xhwang, 2014/03/21 22:33:28]

Done.

+// supports it.
 BASE_EXPORT NativeLibrary LoadNativeLibrary(const FilePath& library_path,
-                                            std::string* error);
+                                            NativeLibraryLoadError* error);
 
 #if defined(OS_WIN)
 // Loads a native library from disk.  Release it with UnloadNativeLibrary when