Make the subresource filter support subdomain anchor matching.

components/subresource_filter/core/common/fuzzy_pattern_matching.h

Index: components/subresource_filter/core/common/fuzzy_pattern_matching.h
diff --git a/components/subresource_filter/core/common/fuzzy_pattern_matching.h b/components/subresource_filter/core/common/fuzzy_pattern_matching.h
index 586190abd54ae240b35003a1d8173d1f9c9e9a5f..15e9fe792627a1f943403305a77e06bb3d35a2d0 100644
--- a/components/subresource_filter/core/common/fuzzy_pattern_matching.h
+++ b/components/subresource_filter/core/common/fuzzy_pattern_matching.h
@@ -5,9 +5,9 @@
 // The separator placeholder '^' symbol is used in subpatterns to match any
 // separator character, which is any ASCII symbol except letters, digits, and
 // the following: '_', '-', '.', '%'. Note that the separator placeholder
-// character '^' is itself a separator, as well as '\0'. In addition, a
-// separator placeholder at the end of the pattern can be matched by the end of
-// |text|.
+// character '^' is itself a separator, as well as '\0'.
+// TODO(pkalinnikov): In addition, a separator placeholder at the end of the
+// pattern can be matched by the end of |text|.
 //
 // We define a fuzzy occurrence as an occurrence of a |subpattern| in |text|
 // such that all its non-placeholder characters are equal to the corresponding