Bug 1489170 - fix C linkage in Moz2DImageRender. r=me

gfx/webrender_bindings/Moz2DImageRenderer.cpp

@@ -239,6 +239,8 @@ DeleteBlobFont(WrFontInstanceKey aKey)
   }
 }
 
+} // extern
+
 static RefPtr<UnscaledFont>
 GetUnscaledFont(Translator* aTranslator, WrFontKey aKey)
 {
@@ -455,6 +457,11 @@ static bool Moz2DRenderCallback(const Range<const uint8_t> aBlob,
   return ret;
 }
 
+} // namespace
+} // namespace
+
+extern "C" {
+
 bool wr_moz2d_render_cb(const mozilla::wr::ByteSlice blob,
                         uint32_t width, uint32_t height,
                         mozilla::wr::ImageFormat aFormat,
@@ -474,6 +481,3 @@ bool wr_moz2d_render_cb(const mozilla::wr::ByteSlice blob,
 
 } // extern
 
-} // namespace
-} // namespace
-