Safeguard against crash-looping if subresource filter rule indexing fails.

components/subresource_filter/core/browser/subresource_filter_constants.h

Index: components/subresource_filter/core/browser/subresource_filter_constants.h
diff --git a/components/subresource_filter/core/browser/subresource_filter_constants.h b/components/subresource_filter/core/browser/subresource_filter_constants.h
index a37d38c60797f6f72e7790847d598a1b43ee0eae..0d52ad778bff9b35b85f7ae1ccc096fef43fdbee 100644
--- a/components/subresource_filter/core/browser/subresource_filter_constants.h
+++ b/components/subresource_filter/core/browser/subresource_filter_constants.h
@@ -13,6 +13,9 @@ namespace subresource_filter {
 // contains all files and subdirectories related to the subresource filter.
 extern const base::FilePath::CharType kTopLevelDirectoryName[];
 
+// Paths under |kTopLevelDirectoryName|
+// ------------------------------------
+
 // The name of the subdirectory under the top-level directory that stores
 // versions of indexed rulesets. Files that belong to an IndexedRulesetVersion
 // are stored under /format_version/content_version/.
@@ -22,12 +25,19 @@ extern const base::FilePath::CharType kIndexedRulesetBaseDirectoryName[];
 // versions of unindexed rulesets downloaded through the component updater.
 extern const base::FilePath::CharType kUnindexedRulesetBaseDirectoryName[];
 
+// Paths under IndexedRulesetVersion::GetSubdirectoryPathForVersion
+// ----------------------------------------------------------------
+
 // The name of the file that actually stores the ruleset contents.
 extern const base::FilePath::CharType kRulesetDataFileName[];
 
 // The name of the applicable license file, if any, stored next to the ruleset.
 extern const base::FilePath::CharType kLicenseFileName[];
 
+// The name of the sentinel file that is temporarily stored to indicate that the
+// ruleset is being indexed.
+extern const base::FilePath::CharType kSentinelFileName[];
+
 }  // namespace subresource_filter
 
 #endif  // COMPONENTS_SUBRESOURCE_FILTER_CORE_BROWSER_SUBRESOURCE_FILTER_CONSTANTS_H_