Histogram versions and extended error codes for SQLite databases.

sql/connection.h

Index: sql/connection.h
diff --git a/sql/connection.h b/sql/connection.h
index cebc774fa57a2f80b4600edeae5dddb55e343c98..ffc3d65be287c4787358035fdef2440ad3a2bb71 100644
--- a/sql/connection.h
+++ b/sql/connection.h
@@ -146,13 +146,17 @@ class SQL_EXPORT Connection {
     error_delegate_.reset(delegate);
   }
 
-  // SQLite error codes for errors on all connections are logged to
-  // enum histogram "Sqlite.Error".  Setting this additionally logs
-  // errors to the histogram |name|.
-  void set_error_histogram_name(const std::string& name) {
-    error_histogram_name_ = name;
+  // Set this prefix to enable additional connection-type
+  // histogramming for SQLite error codes and database version
+  // numbers.
+  void set_histogram_prefix(const std::string& prefix) {
+    histogram_prefix_ = prefix;
   }
 
+  // Record a sparse UMA histogram sample under |histogram_prefix_|+|suffix|.
+  // If |histogram_prefix_| is empty, no histogram is recorded.
+  void AddSparseHistogram(const std::string& suffix, size_t sample) const;
+
   // Initialization ------------------------------------------------------------
 
   // Initializes the SQL connection for the given file, returning true if the
@@ -497,8 +501,8 @@ class SQL_EXPORT Connection {
   // commands or statements. It can be null which means default handling.
   scoped_ptr<ErrorDelegate> error_delegate_;
 
-  // Auxiliary error-code histogram.
-  std::string error_histogram_name_;
+  // Prefix for auxiliary histograms.
+  std::string histogram_prefix_;
 
   DISALLOW_COPY_AND_ASSIGN(Connection);
 };