Add metrics for schemes of content setting exceptions

components/content_settings/core/common/content_settings_pattern.h

Index: components/content_settings/core/common/content_settings_pattern.h
diff --git a/components/content_settings/core/common/content_settings_pattern.h b/components/content_settings/core/common/content_settings_pattern.h
index f85c648bfc036aa9ac0261d0aa3cb62ed0d5318f..d0c59db530e0a5944671863be4dd540cf24a340e 100644
--- a/components/content_settings/core/common/content_settings_pattern.h
+++ b/components/content_settings/core/common/content_settings_pattern.h
@@ -53,6 +53,19 @@ class ContentSettingsPattern {
     DISJOINT_ORDER_PRE = 2,
   };
 
+  // This enum is used to back an UMA histogram, the order of existing values
+  // should not be changed. New values should only append before SCHEME_MAX.
+  // Also keep it consistent with kSchemeNames in content_settings_pattern.cc.
+  enum SchemeType {
+    SCHEME_WILDCARD,
+    SCHEME_OTHER,
+    SCHEME_HTTP,
+    SCHEME_HTTPS,
+    SCHEME_FILE,
+    SCHEME_CHROMEEXTENSION,
+    SCHEME_MAX,
+  };
+
   struct PatternParts {
     PatternParts();
     PatternParts(const PatternParts& other);
@@ -170,6 +183,9 @@ class ContentSettingsPattern {
   // Returns a std::string representation of this pattern.
   std::string ToString() const;
 
+  // Returns scheme type of pattern.
+  ContentSettingsPattern::SchemeType GetScheme() const;
+
   // Compares the pattern with a given |other| pattern and returns the
   // |Relation| of the two patterns.
   Relation Compare(const ContentSettingsPattern& other) const;