Merge google-perftools r109 (the current contents of third_party/tcmalloc/vendor)

third_party/tcmalloc/chromium/src/base/vdso_support.h

Index: third_party/tcmalloc/chromium/src/base/vdso_support.h
===================================================================
--- third_party/tcmalloc/chromium/src/base/vdso_support.h	(revision 87277)
+++ third_party/tcmalloc/chromium/src/base/vdso_support.h	(working copy)
@@ -30,6 +30,7 @@
 #ifdef HAVE_FEATURES_H
 #include <features.h>   // for __GLIBC__
 #endif
+#include "base/basictypes.h"
 
 // Maybe one day we can rewrite this file not to require the elf
 // symbol extensions in glibc, but for right now we need them.
@@ -39,7 +40,6 @@
 
 #include <stdlib.h>     // for NULL
 #include <link.h>  // for ElfW
-#include "base/basictypes.h"
 
 namespace base {
 
@@ -64,7 +64,7 @@
   // Supports iteration over all dynamic symbols.
   class SymbolIterator {
    public:
-    friend struct VDSOSupport;
+    friend class VDSOSupport;
     const SymbolInfo *operator->() const;
     const SymbolInfo &operator*() const;
     SymbolIterator& operator++();
@@ -147,6 +147,10 @@
   //   kInvalidBase   => value hasn't been determined yet.
   //              0   => there is no VDSO.
   //           else   => vma of VDSO Elf{32,64}_Ehdr.
+  //
+  // When testing with mock VDSO, low bit is set.
+  // The low bit is always available because vdso_base_ is
+  // page-aligned.
   static const void *vdso_base_;
 
   // NOLINT on 'long' because these routines mimic kernel api.