Speed up IdAllocator.

gpu/command_buffer/common/id_allocator.h

Index: gpu/command_buffer/common/id_allocator.h
===================================================================
--- gpu/command_buffer/common/id_allocator.h	(revision 86796)
+++ gpu/command_buffer/common/id_allocator.h	(working copy)
@@ -44,9 +44,14 @@
   // TODO(gman): This would work much better with ranges or a hash table.
   typedef std::set<ResourceId> ResourceIdSet;

[greggman, 2011/05/26 16:25:29]

If were doing this for speed, how about changing this to a hash_set?

Note: you'll have to copy hash_set from base into gpu/common/ as anything in
used in gpu/client can not depend on base.

 
-  ResourceId FindFirstFree() const;
+  // The highest ID on the used list.
+  ResourceId LastUsedId() const;
 
+  // Lowest ID that isn't on the used list. This is slow, use as a last resort.
+  ResourceId FindFirstUnusedId() const;
+
   ResourceIdSet used_ids_;
+  ResourceIdSet free_ids_;
 
   DISALLOW_COPY_AND_ASSIGN(IdAllocator);
 };