Force enable V0 APIs for FilesApp extension w Polymer1.

This patch is a preparation for Shadow DOM V0, Custom Element V0 (CEv0) and HTML Imports removal.
Intent to Deprecate and Remove: http://bit.ly/2RGHe3x
Though we soon make these APIs only available for test by turning the json5 feature flag
from status: "stable" to status: "test", there is browser tests/chrome internal components
that use them.

FilesApp finished migration but it was only for w/o Polymer2.
FilesApp w Polymer1 still needs the APIs for it.
Descussion of flagging was done at previous patch among Jochen and Devlin: crrev.com/c/1405955


Bug: 924873, 911943

Change-Id: I0d3038ce5d21c410e1a055b57752d0df62cf62fb
Reviewed-on: https://chromium-review.googlesource.com/c/1496259Reviewed-by: Ken Rockot <rockot@google.com>
Commit-Queue: Yoichi Osato <yoichio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636714}

extensions/renderer/dispatcher.cc

@@ -900,6 +900,21 @@ void Dispatcher::OnActivateExtension(const std::string& extension_id) {
     blink::WebRuntimeFeatures::EnableCustomElementsV0(true);
     blink::WebRuntimeFeatures::EnableHTMLImports(true);
   }
+  // FilesApp support. crbug.com/924873
+  // For Polymer1, we still need v0 APIs.
+  // Extensions IDs from src/chrome/browser/chromeos/file_manager/app_id.h.
+  if (!base::FeatureList::IsEnabled(features::kWebUIPolymer2) &&
+      (extension_id == "hhaomjibdihmijegdhdafkllkbggdgoj" ||
+       extension_id == "jcgeabjmjgoblfofpppfkcoakmfobdko" ||
+       extension_id == "nlkncpkkdoccmpiclbokaimcnedabhhm" ||
+       extension_id == "cjbfomnbifhcdnihkgipgfcihmgjfhbf" ||
+       extension_id == "mmfbcljfglbokpmkimbfghdkjmjhdgbg" ||
+       extension_id == "pmfjbimdmchhbnneeidfognadeopoehp" ||
+       extension_id == "dmboannefpncccogfdikhmhpmdnddgoe")) {
+    blink::WebRuntimeFeatures::EnableShadowDOMV0(true);
+    blink::WebRuntimeFeatures::EnableCustomElementsV0(true);
+    blink::WebRuntimeFeatures::EnableHTMLImports(true);
+  }
 
   InitOriginPermissions(extension);