Use extension-based file picker from CrOS for Aura builds.

chrome/browser/browser_resources.grd

Index: chrome/browser/browser_resources.grd
diff --git a/chrome/browser/browser_resources.grd b/chrome/browser/browser_resources.grd
index 5ef0cc25116e41cebe1189ab612204fe69c732ed..20d86f4ce3d6cff3b7d2b6cd53b095be98a396c2 100644
--- a/chrome/browser/browser_resources.grd
+++ b/chrome/browser/browser_resources.grd
@@ -149,10 +149,12 @@
         <include name="IDR_CHROMEVOX_MANIFEST" file="resources\access_chromevox\manifest.json" type="BINDATA" />
         <!-- Enterprise enrollment dialog -->
         <include name="IDR_ENTERPRISE_ENROLLMENT_HTML" file="policy\resources\enrollment.html" flattenhtml="true" type="BINDATA" />
-        <include name="IDR_FILEMANAGER_MANIFEST" file="resources\file_manager\manifest.json" type="BINDATA" />
         <include name="IDR_GAIA_AUTH_MANIFEST" file="resources\gaia_auth\manifest.json" type="BINDATA" />
         <include name="IDR_GAIA_TEST_AUTH_MANIFEST" file="resources\gaia_auth\manifest_test.json" type="BINDATA" />
       </if>
+      <if expr="pp_ifdef('file_manager_extension')">
+        <include name="IDR_FILEMANAGER_MANIFEST" file="resources\file_manager\manifest.json" type="BINDATA" />
+      </if>
       <if expr="pp_ifdef('chromeos') and pp_ifdef('_google_chrome')">
         <include name="IDR_HELP_MANIFEST" file="resources\help_app\manifest.json" type="BINDATA" />
       </if>