Revert of Gallery: use shadow dom with Polymer. (patchset #1 id:1 of...

Revert of Gallery: use shadow dom with Polymer. (patchset #1 id:1 of https://codereview.chromium.org/1168333002/)

Reason for revert:
All of Gallery Material Redesign will happen in M46.

Original issue's description:
> Gallery: use shadow dom with Polymer.
>
> BUG=488227
> TEST=none
>
> Committed: https://crrev.com/f17dc18bc3dd133d2be1c92d2f4e3c0b05d4d9b1
> Cr-Commit-Position: refs/heads/master@{#333449}

TBR=fukino@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=488227

Review URL: https://codereview.chromium.org/1172533003

Cr-Commit-Position: refs/heads/master@{#333659}

ui/file_manager/file_manager/manifest.json

@@ -156,7 +156,6 @@
     "common/js/metrics_events.js",
     "common/js/metrics.js",
     "common/js/path_util.js",
-    "common/js/polymer_config.js",
     "common/js/util.js",
     "common/js/volume_manager_common.js",
     "foreground/js/metadata/byte_reader.js",

ui/file_manager/gallery/gallery.html

@@ -12,7 +12,6 @@
   <link rel="stylesheet" href="../file_manager/foreground/css/share_dialog.css">
   <link rel="stylesheet" href="css/gallery.css">
 
-  <script src="chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/common/js/polymer_config.js"></script>
   <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 
   <!-- Don't load gallery_scripts.js when flattening is disabled -->