Fix StatsTable::RegisterThread so that it doesn't crash if shared memory...

base/stats_table.cc

Index: base/stats_table.cc
===================================================================
--- base/stats_table.cc	(revision 18166)
+++ base/stats_table.cc	(working copy)
@@ -287,6 +287,8 @@
 
 int StatsTable::RegisterThread(const std::string& name) {
   int slot = 0;
+  if (!impl_)
+    return 0;
 
   // Registering a thread requires that we lock the shared memory
   // so that two threads don't grab the same slot.  Fortunately,
@@ -298,8 +300,6 @@
       return 0;
     }
 
-    DCHECK(impl_);
-
     // We have space, so consume a column in the table.
     std::string thread_name = name;
     if (name.empty())
@@ -448,8 +448,6 @@
 }
 
 int StatsTable::AddCounter(const std::string& name) {
-  DCHECK(impl_);
-
   if (!impl_)
     return 0;