Update the tcmalloc vendor branch to r144 (gperftools 2.0), and README.chromium.

third_party/tcmalloc/vendor/src/stacktrace_x86-inl.h

 // Copyright (c) 2005, Google Inc.
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 // notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
@@ skipping 46 matching lines @@
 #include <stdint.h>   // for uintptr_t
 #endif
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 #ifdef HAVE_MMAP
 #include <sys/mman.h> // for msync
 #include "base/vdso_support.h"
 #endif
 
-#include "google/stacktrace.h"
+#include "gperftools/stacktrace.h"
 
 #if defined(__linux__) && defined(__i386__) && defined(__ELF__) && defined(HAVE_MMAP)
 // Count "push %reg" instructions in VDSO __kernel_vsyscall(),
 // preceeding "syscall" or "sysenter".
 // If __kernel_vsyscall uses frame pointer, answer 0.
 //
 // kMaxBytes tells how many instruction bytes of __kernel_vsyscall
 // to analyze before giving up. Up to kMaxBytes+1 bytes of
 // instructions could be accessed.
 //
@@ skipping 153 matching lines @@
   if (STRICT_UNWINDING) {
     // With the stack growing downwards, older stack frame must be
     // at a greater address that the current one.
     if (new_sp <= old_sp) return NULL;
     // Assume stack frames larger than 100,000 bytes are bogus.
     if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000) return NULL;
   } else {
     // In the non-strict mode, allow discontiguous stack frames.
     // (alternate-signal-stacks for example).
     if (new_sp == old_sp) return NULL;
-    // And allow frames upto about 1MB.
-    if ((new_sp > old_sp)
-        && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000)) return NULL;
+    if (new_sp > old_sp) {
+      // And allow frames upto about 1MB.
+      const uintptr_t delta = (uintptr_t)new_sp - (uintptr_t)old_sp;
+      const uintptr_t acceptable_delta = 1000000;
+      if (delta > acceptable_delta) {
+        return NULL;
+      }
+    }
   }
   if ((uintptr_t)new_sp & (sizeof(void *) - 1)) return NULL;
 #ifdef __i386__
   // On 64-bit machines, the stack pointer can be very close to
   // 0xffffffff, so we explicitly check for a pointer into the
   // last two pages in the address space
   if ((uintptr_t)new_sp >= 0xffffe000) return NULL;
 #endif
 #ifdef HAVE_MMAP
   if (!STRICT_UNWINDING) {
@@ skipping 83 matching lines @@
         // A frame-size of 0 is used to indicate unknown frame size.
         sizes[n] = 0;
       }
 #endif
       n++;
     }
     sp = next_sp;
   }
   return n;
 }