Typo spelling in comment corrected.

base/histogram.h

Index: base/histogram.h
===================================================================
--- base/histogram.h	(revision 35302)
+++ base/histogram.h	(working copy)
@@ -432,7 +432,7 @@
   // ASCII version of original name given to the constructor.  All identically
   // named instances will  be coalesced cross-project TODO(jar).
   // If a user needs one histogram name to be called by several places in a
-  // single process, a central function should be defined by teh user, which
+  // single process, a central function should be defined by the user, which
   // defins the single declared instance of the named histogram.
   const std::string histogram_name_;
   Sample declared_min_;  // Less than this goes into counts_[0]