Refer internal PIEX library by using <include> tag in piex.pexe.txt.

ui/file_manager/file_manager_resources.grd

Index: ui/file_manager/file_manager_resources.grd
diff --git a/ui/file_manager/file_manager_resources.grd b/ui/file_manager/file_manager_resources.grd
index 6923c95b61b131ab106daf5536905d87ed1a01e5..9a94fc91b1631c7cde9bbd6d8a9abe2e35e6d5d3 100644
--- a/ui/file_manager/file_manager_resources.grd
+++ b/ui/file_manager/file_manager_resources.grd
@@ -189,15 +189,12 @@
         <include name="IDR_IMAGE_LOADER_MANIFEST" file="image_loader/manifest.json" type="BINDATA" />
         <include name="IDR_IMAGE_LOADER_BACKGROUND_JS" file="image_loader/background_scripts.js" flattenhtml="true" type="BINDATA" />
         <include name="IDR_IMAGE_LOADER_CLIENT_JS" file="image_loader/image_loader_client.js" type="BINDATA" />
+
         <!-- Internal resources. -->
-        <if expr="not _google_chrome">
-          <include name="IDR_IMAGE_LOADER_PIEX_LOADER_PNACL" file="image_loader/piex/piex.pexe.txt" type="BINDATA" />
-        </if>
         <if expr="_google_chrome">
-          <!-- This entry overrides IDR_IMAGE_LOADER_PIEX_LOADER_PNACL with content of ../internal/piex/piex.pexe. -->
-          <include name="IDR_IMAGE_LOADER_PIEX_LOADER_PNACL" file="internal/piex/piex.pexe" type="BINDATA" />
+          <include name="IDR_IMAGE_LOADER_PIEX_LOADER_MANIFEST" file="image_loader/piex/piex.nmf.txt" type="BINDATA" />
+          <include name="IDR_IMAGE_LOADER_PIEX_LOADER_PNACL" flattenhtml="true" file="image_loader/piex/piex.pexe.txt" type="BINDATA" />
         </if>
-        <include name="IDR_IMAGE_LOADER_PIEX_LOADER_MANIFEST" file="image_loader/piex/piex.nmf.txt" type="BINDATA" />
       </if>
     </includes>
   </release>