Add/improve a bunch of comments...

chrome/common/chrome_constants.h

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // A handful of resource-like constants related to the Chrome application.
 
 #ifndef CHROME_COMMON_CHROME_CONSTANTS_H_
 #define CHROME_COMMON_CHROME_CONSTANTS_H_
 #pragma once
 
@@ skipping 63 matching lines @@
 extern const unsigned int kMaxRendererProcessCount;
 extern const int kStatsMaxThreads;
 extern const int kStatsMaxCounters;
 
 // The maximum number of characters of the document's title that we're willing
 // to accept in the browser process.
 extern const size_t kMaxTitleChars;
 
 extern const bool kRecordModeEnabled;
 
+// Most sequence numbers are used by a renderer when responding to a browser
+// request for histogram data.  This reserved number is used when a renderer
+// sends an unprovoked update, such as after a page has been loaded.  Using
+// this reserved constant avoids any chance of confusion with a response having
+// a browser-supplied sequence number.
 extern const int kHistogramSynchronizerReservedSequenceNumber;
 
 // The maximum number of session history entries per tab.
 extern const int kMaxSessionHistoryEntries;
 
 // The language code used when the language of a page could not be detected.
 // (Matches what the CLD -Compact Language Detection- library reports.)
 extern const char* const kUnknownLanguageCode;
 
 }  // namespace chrome
 
 #endif  // CHROME_COMMON_CHROME_CONSTANTS_H_