Add metrics for schemes of content setting exceptions

Add a uma metric to collect data for schemes (http/https/file/chrome-extension) of
content setting exceptions.

BUG=621724

Review-Url: https://codereview.chromium.org/2226643002
Cr-Commit-Position: refs/heads/master@{#411245}

components/content_settings/core/browser/host_content_settings_map.cc

@@ -187,7 +187,7 @@ HostContentSettingsMap::HostContentSettingsMap(PrefService* prefs,
 
   MigrateKeygenSettings();
   MigrateDomainScopedSettings(false);
-  RecordNumberOfExceptions();
+  RecordExceptionMetrics();
 }
 
 // static
@@ -600,7 +600,7 @@ base::WeakPtr<HostContentSettingsMap> HostContentSettingsMap::GetWeakPtr() {
   return weak_ptr_factory_.GetWeakPtr();
 }
 
-void HostContentSettingsMap::RecordNumberOfExceptions() {
+void HostContentSettingsMap::RecordExceptionMetrics() {
   for (const content_settings::WebsiteSettingsInfo* info :
        *content_settings::WebsiteSettingsRegistry::GetInstance()) {
     ContentSettingsType content_type = info->type();
@@ -610,6 +610,17 @@ void HostContentSettingsMap::RecordNumberOfExceptions() {
     GetSettingsForOneType(content_type, std::string(), &settings);
     size_t num_exceptions = 0;
     for (const ContentSettingPatternSource& setting_entry : settings) {
+      // Skip default settings.
+      if (setting_entry.primary_pattern == ContentSettingsPattern::Wildcard() &&
+          setting_entry.secondary_pattern ==
+              ContentSettingsPattern::Wildcard()) {
+        continue;
+      }
+
+      UMA_HISTOGRAM_ENUMERATION("ContentSettings.ExceptionScheme",
+                                setting_entry.primary_pattern.GetScheme(),
+                                ContentSettingsPattern::SCHEME_MAX);
+
       if (setting_entry.source == "preference")
         ++num_exceptions;
     }

components/content_settings/core/browser/host_content_settings_map.h

@@ -329,8 +329,8 @@ class HostContentSettingsMap : public content_settings::Observer,
   // leave in some code to remove old-format settings for a long time.
   void MigrateKeygenSettings();
 
-  // Collect UMA data about the number of exceptions.
-  void RecordNumberOfExceptions();
+  // Collect UMA data of exceptions.
+  void RecordExceptionMetrics();
 
   // Adds content settings for |content_type| and |resource_identifier|,
   // provided by |provider|, into |settings|. If |incognito| is true, adds only

components/content_settings/core/common/content_settings_pattern.cc

@@ -21,6 +21,19 @@ namespace {
 // The component supports only one scheme for simplicity.
 const char* non_port_non_domain_wildcard_scheme = NULL;
 
+// Keep it consistent with enum SchemeType in content_settings_pattern.h.
+const char* const kSchemeNames[] = {
+  "wildcard",
+  "other",
+  url::kHttpScheme,
+  url::kHttpsScheme,
+  url::kFileScheme,
+  "chrome-extension",
+};
+
+static_assert(arraysize(kSchemeNames) == ContentSettingsPattern::SCHEME_MAX,
+              "kSchemeNames should have SCHEME_MAX elements");
+
 std::string GetDefaultPort(const std::string& scheme) {
   if (scheme == url::kHttpScheme)
     return "80";
@@ -590,6 +603,17 @@ std::string ContentSettingsPattern::ToString() const {
     return std::string();
 }
 
+ContentSettingsPattern::SchemeType ContentSettingsPattern::GetScheme() const {
+  if (parts_.is_scheme_wildcard)
+    return SCHEME_WILDCARD;
+
+  for (size_t i = 2; i < arraysize(kSchemeNames); ++i) {
+    if (parts_.scheme == kSchemeNames[i])
+      return static_cast<SchemeType>(i);
+  }
+  return SCHEME_OTHER;
+}
+
 ContentSettingsPattern::Relation ContentSettingsPattern::Compare(
     const ContentSettingsPattern& other) const {
   // Two invalid patterns are identical in the way they behave. They don't match

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);
@@ -178,6 +191,9 @@ 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;

components/content_settings/core/common/content_settings_pattern_unittest.cc

@@ -808,4 +808,22 @@ TEST(ContentSettingsPatternTest, MigrateFromDomainToOrigin) {
       ContentSettingsPattern::FromString("https://[*.]google.com:443"),
       &origin_pattern));
   EXPECT_EQ("https://google.com:443", origin_pattern.ToString());
+}
+
+TEST(ContentSettingsPatternTest, Schemes) {
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_HTTP,
+            Pattern("http://www.example.com").GetScheme());
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_HTTPS,
+            Pattern("https://www.example.com").GetScheme());
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_FILE,
+            Pattern("file:///tmp/file.html").GetScheme());
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_CHROMEEXTENSION,
+            Pattern("chrome-extension://peoadpeiejnhkmpaakpnompolbglelel/")
+                .GetScheme());
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_WILDCARD,
+            Pattern("192.168.0.1").GetScheme());
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_WILDCARD,
+            Pattern("www.example.com").GetScheme());
+  EXPECT_EQ(ContentSettingsPattern::SCHEME_OTHER,
+            Pattern("filesystem:http://www.google.com/temporary/").GetScheme());
 }

tools/metrics/histograms/histograms.xml

@@ -6604,6 +6604,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ContentSettings.ExceptionScheme" enum="ContentSettingScheme">
+  <owner>lshang@chromium.org</owner>
+  <summary>
+    Records the schemes of content setting exceptions at browser start. Each
+    exception provides one sample.
+  </summary>
+</histogram>
+
 <histogram name="ContentSettings.LastSettingParsed" enum="LastSettingParsed">
   <obsolete>
     Deprecated 2015-10-05 in Issue 433475. Histogram was used temorarily for
@@ -71028,6 +71036,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="3" label="Clicked 'Learn more'"/>
 </enum>
 
+<enum name="ContentSettingScheme" type="int">
+  <int value="0" label="(wildcard)"/>
+  <int value="1" label="(other)"/>
+  <int value="2" label="http"/>
+  <int value="3" label="https"/>
+  <int value="4" label="file"/>
+  <int value="5" label="chrome-extension"/>
+</enum>
+
 <enum name="ContentType" type="int">
   <int value="-1" label="Invalid setting"/>
   <int value="0" label="Cookies setting"/>