Fix typo in tools/grokdump.py. Stack pointer on x86 is esp not rbp.

R=fschneider@chromium.org

Review URL: http://codereview.chromium.org/9069001

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10316 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

tools/grokdump.py

@@ -486,7 +486,7 @@ class MinidumpReader(object):
     if self.arch == MD_CPU_ARCHITECTURE_AMD64:
       return self.exception_context.rsp
     elif self.arch == MD_CPU_ARCHITECTURE_X86:
-      return self.exception_context.rbp
+      return self.exception_context.esp
 
   def FormatIntPtr(self, value):
     if self.arch == MD_CPU_ARCHITECTURE_AMD64: