Decompose //extensions/browser/BUILD.gn

extensions/browser/install/BUILD.gn

Index: extensions/browser/install/BUILD.gn
diff --git a/components/subresource_filter/core/common/flat/BUILD.gn b/extensions/browser/install/BUILD.gn
similarity index 62%
copy from components/subresource_filter/core/common/flat/BUILD.gn
copy to extensions/browser/install/BUILD.gn
index 195c0cd11e02c6f6711ae1150e1c73aaa52a374c..b453a7954c54c79474f027fc4982146e72a14f50 100644
--- a/components/subresource_filter/core/common/flat/BUILD.gn
+++ b/extensions/browser/install/BUILD.gn
@@ -2,10 +2,10 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//third_party/flatbuffers/flatbuffer.gni")
-
-flatbuffer("flatbuffer") {
+source_set("install") {
   sources = [
-    "rules.fbs",
+    "crx_install_error.h",
+    "extension_install_ui.cc",
+    "extension_install_ui.h",
   ]
 }