Various optimizations to reduce the number of temporary allocations.

chrome/browser/themes/browser_theme_pack.h

Index: chrome/browser/themes/browser_theme_pack.h
diff --git a/chrome/browser/themes/browser_theme_pack.h b/chrome/browser/themes/browser_theme_pack.h
index effba56c166599aab5ef5163127d2d172eaf5c25..8d5bdaa823f96db55f48213d158bc6e23c8ef88a 100644
--- a/chrome/browser/themes/browser_theme_pack.h
+++ b/chrome/browser/themes/browser_theme_pack.h
@@ -67,9 +67,8 @@ class BrowserThemePack : public CustomThemeSupplier {
   static scoped_refptr<BrowserThemePack> BuildFromDataPack(
       const base::FilePath& path, const std::string& expected_id);
 
-  // Returns the set of image IDRs which can be overwritten by a user provided
-  // theme.
-  static void GetThemeableImageIDRs(std::set<int>* result);
+  // Returns true if an IDR exists.
+  static bool IsThemeableImageIDRs(int id);

[Peter Kasting, 2014/12/03 21:21:03]

This name is confusing.  Why does it have an 's' on the end?  Why does the
comment just talk about the IDR "existing" when that's not what the function
does?  Seems more like this should be:

  // Returns whether the specified identifier is one of the images we persist in
the data pack.
  static bool IsPersistentImageID(int id);

[Georges Khalil, 2014/12/03 21:58:32]

Done.

 
   // Builds a data pack on disk at |path| for future quick loading by
   // BuildFromDataPack(). Often (but not always) called from the file thread;