Files.app: Enable PIEX loader for official build.

The PIEX library has been submitted to official chrome repository.
The CL let Files.app use the library to load RAW thumbnails.

BUG=396702
TEST=None

Review URL: https://codereview.chromium.org/1034713002

Cr-Commit-Position: refs/heads/master@{#322372}

ui/file_manager/file_manager_resources.grd

@@ -151,7 +151,13 @@
         <include name="IDR_IMAGE_LOADER_CLIENT_JS" file="image_loader/image_loader_client.js" type="BINDATA" />
         <include name="IDR_IMAGE_LOADER_PIEX_LOADER_JS" file="image_loader/piex_loader.js" flattenhtml="true" type="BINDATA" />
         <!-- Internal resources. -->
-        <include name="IDR_IMAGE_LOADER_PIEX_LOADER_PNACL" file="image_loader/piex/piex.pexe.txt" type="BINDATA" />
+        <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" />
+        </if>
         <include name="IDR_IMAGE_LOADER_PIEX_LOADER_MANIFEST" file="image_loader/piex/piex.nmf.txt" type="BINDATA" />
       </if>
     </includes>