[StartSurface] Include 'ss_explore_scroll_container.xml' only when feed is enabled

to suppress 'UnusedResources' lint warning when feed is disabled.

Bug: 982018
Change-Id: I841104a65ed7f1f7bf02b2bd4fdc40ed90505ac6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1782718Reviewed-by: Theresa  <twellington@chromium.org>
Commit-Queue: Ganggui Tang <gogerald@chromium.org>
Auto-Submit: Ganggui Tang <gogerald@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693183}

chrome/android/features/start_surface/internal/BUILD.gn

@@ -68,6 +68,9 @@ java_strings_grd("java_strings_grd") {
 
 android_resources("java_resources") {
   resource_dirs = [ "java/res" ]
+  if (enable_feed_in_chrome) {
+    resource_dirs += [ "java/explore_res" ]
+  }
   deps = [
     ":java_strings_grd",
     "//chrome/android:chrome_app_java_resources",