Modify dark_mode watchlist.

This patch modifies watchlists to include files with dark_mode anywhere
in the filename and to include dark_mode files from cc/*.

Bug: None
Change-Id: I99ac814e4e79bd1a4ad1cadf380d20c677cfae85
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2472677Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Prashant Nevase <prashant.n@samsung.com>
Cr-Commit-Position: refs/heads/master@{#817121}

WATCHLISTS

@@ -905,7 +905,8 @@
                   'chrome/browser/android/customtabs/',
     },
     'dark_mode': {
-      'filepath': 'third_party/blink/renderer/platform/graphics/dark_mode*',
+      'filepath': 'cc/*/*dark_mode*|'\
+                  'third_party/blink/renderer/platform/graphics/*dark_mode*',
     },
     'data_decoder': {
       'filepath': 'services/data_decoder/',