Add UMA statistics for tracking session storage database opening failures.

webkit/dom_storage/session_storage_database.cc

Index: webkit/dom_storage/session_storage_database.cc
diff --git a/webkit/dom_storage/session_storage_database.cc b/webkit/dom_storage/session_storage_database.cc
index b22ea30296bd01e45593eb5e10f440c027ead4f8..d3613d4cd7eab8984d63d0420cf146c5270967bb 100644
--- a/webkit/dom_storage/session_storage_database.cc
+++ b/webkit/dom_storage/session_storage_database.cc
@@ -6,6 +6,7 @@
 
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/stringprintf.h"
 #include "base/string_number_conversions.h"
 #include "base/utf_string_conversions.h"
@@ -16,6 +17,19 @@
 #include "third_party/leveldatabase/src/include/leveldb/options.h"
 #include "third_party/leveldatabase/src/include/leveldb/write_batch.h"
 
+#define SESSION_STORAGE_UMA_NAME "SessionStorageDatabase.Open"
+
+namespace {
+
+enum SessionStorageUMA {
+  SESSION_STORAGE_UMA_SUCCESS,
+  SESSION_STORAGE_UMA_RECREATED,
+  SESSION_STORAGE_UMA_FAIL,
+  SESSION_STORAGE_UMA_MAX
+};
+
+}  // namespace
+
 // Layout of the database:
 // | key                            | value                              |
 // -----------------------------------------------------------------------
@@ -286,10 +300,20 @@ bool SessionStorageDatabase::LazyOpen(bool create_if_needed) {
     if (!s.ok()) {
       LOG(WARNING) << "Failed to open leveldb in " << file_path_.value()
                    << ", error: " << s.ToString();
+      UMA_HISTOGRAM_ENUMERATION(SESSION_STORAGE_UMA_NAME,
+                                SESSION_STORAGE_UMA_FAIL,
+                                SESSION_STORAGE_UMA_MAX);
       DCHECK(db == NULL);
       db_error_ = true;
       return false;
     }
+    UMA_HISTOGRAM_ENUMERATION(SESSION_STORAGE_UMA_NAME,
+                              SESSION_STORAGE_UMA_RECREATED,
+                              SESSION_STORAGE_UMA_MAX);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION(SESSION_STORAGE_UMA_NAME,
+                              SESSION_STORAGE_UMA_SUCCESS,
+                              SESSION_STORAGE_UMA_MAX);
   }
   db_.reset(db);
   return true;