IndexedDB: Add histograms for key type

third_party/WebKit/Source/modules/indexeddb/IDBKey.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 45 matching lines @@
   static IDBKey* createDate(double date) { return new IDBKey(DateType, date); }
 
   static IDBKey* createArray(const KeyArray& array) {
     return new IDBKey(array);
   }
 
   ~IDBKey();
   DECLARE_TRACE();
 
   // In order of the least to the highest precedent in terms of sort order.
+  // Also used for UMA. Append only.

[Mark P, 2017/02/07 19:12:22]

Please follow the comments and = guidelines here.
https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histo...
Also, generally it's better practice to make the max bigger than the last
element so you can expand this histogram correctly later.

[jsbell, 2017/02/07 19:54:56]

Done.

   enum Type {
     InvalidType = 0,
     ArrayType,
     BinaryType,
     StringType,
     DateType,
     NumberType,
-    MinType
+    TypeEnumMax = NumberType
   };
 
   Type getType() const { return m_type; }
   bool isValid() const;
 
   const KeyArray& array() const {
     ASSERT(m_type == ArrayType);
     return m_array;
   }
 
@@ skipping 36 matching lines @@
   const Type m_type;
   const KeyArray m_array;
   RefPtr<SharedBuffer> m_binary;
   const String m_string;
   const double m_number = 0;
 };
 
 }  // namespace blink
 
 #endif  // IDBKey_h