kThemePackVersion comment should mention theme cache flushing.

chrome/browser/themes/browser_theme_pack.cc

Index: chrome/browser/themes/browser_theme_pack.cc
diff --git a/chrome/browser/themes/browser_theme_pack.cc b/chrome/browser/themes/browser_theme_pack.cc
index 931fd46bde056834b68d9bf23b6de6988ee34c06..069bf320318bc49c90eede7178e8d37dd49f6bdd 100644
--- a/chrome/browser/themes/browser_theme_pack.cc
+++ b/chrome/browser/themes/browser_theme_pack.cc
@@ -48,7 +48,7 @@ namespace {
 
 // Version number of the current theme pack. We just throw out and rebuild
 // theme packs that aren't int-equal to this. Increment this number if you
-// change default theme assets.
+// change default theme assets or otherwise need to flush the theme image cache.

[Evan Stade, 2016/03/17 01:06:51]

actually the "cache" is a bit vague here. Can we say something like "or if you
need themes to recreate their generated images."

[shrike, 2016/03/17 20:59:15]

I'm OK with that, except I think it should explicitly mention that these images
are cached. Please let me know what you think of my edit.

 const int kThemePackVersion = 40;
 
 // IDs that are in the DataPack won't clash with the positive integer