Update the tcmalloc vendor branch to r144 (gperftools 2.0).

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

Index: third_party/tcmalloc/vendor/src/stacktrace_x86-inl.h
diff --git a/third_party/tcmalloc/vendor/src/stacktrace_x86-inl.h b/third_party/tcmalloc/vendor/src/stacktrace_x86-inl.h
index a140ab6b01754230c745e84d581993ef04f524fb..9d76342a14484c29cb41ffc221e7129cdfdccd47 100644
--- a/third_party/tcmalloc/vendor/src/stacktrace_x86-inl.h
+++ b/third_party/tcmalloc/vendor/src/stacktrace_x86-inl.h
@@ -64,7 +64,7 @@ typedef ucontext ucontext_t;
 #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(),
@@ -238,9 +238,14 @@ static void **NextStackFrame(void **old_sp, const void *uc) {
     // 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__