Don't allow for error in ProgramImpl::save.

Refactoring cleanup patch only.

BUG=angleproject:1897

Change-Id: I6d12de5dab16ead9684886a1cf15b570e3c98156
Reviewed-on: https://chromium-review.googlesource.com/522871
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libANGLE/renderer/null/ProgramNULL.h b/src/libANGLE/renderer/null/ProgramNULL.h
index b6e1e63..2be4b30 100644
--- a/src/libANGLE/renderer/null/ProgramNULL.h
+++ b/src/libANGLE/renderer/null/ProgramNULL.h
@@ -24,7 +24,7 @@
     LinkResult load(const gl::Context *context,
                     gl::InfoLog &infoLog,
                     gl::BinaryInputStream *stream) override;
-    gl::Error save(gl::BinaryOutputStream *stream) override;
+    void save(gl::BinaryOutputStream *stream) override;
     void setBinaryRetrievableHint(bool retrievable) override;
     void setSeparable(bool separable) override;