Replace HistoryQuickProvider protobuf-based caching with an SQLite-based database.

sql/diagnostic_error_delegate.h

Index: sql/diagnostic_error_delegate.h
===================================================================
--- sql/diagnostic_error_delegate.h	(revision 151481)
+++ sql/diagnostic_error_delegate.h	(working copy)
@@ -12,6 +12,10 @@
 
 namespace sql {
 
+// The histogram values from sqlite result codes currently range from 1 to 26
+// but 50 gives them room to grow.
+static const int kMaxSqliteError = 50;
+
 // This class handles the exceptional sqlite errors that we might encounter
 // if for example the db is corrupted. Right now we just generate a UMA
 // histogram for release and an assert for debug builds.
@@ -39,9 +43,7 @@
     // Trim off the extended error codes.
     error &= 0xff;
 
-    // The histogram values from sqlite result codes go currently from 1 to
-    // 26 currently but 50 gives them room to grow.
-    UMA_HISTOGRAM_ENUMERATION(UniqueT::name(), error, 50);
+    UMA_HISTOGRAM_ENUMERATION(UniqueT::name(), error, kMaxSqliteError);
   }
 };