Fix to use ucontext_t in unwind.h.

third_party/tcmalloc/chromium/src/getpc.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 157 matching lines @@
 #include "base/logging.h"   // for RAW_LOG
 #ifndef HAVE_CYGWIN_SIGNAL_H
 typedef int ucontext_t;
 #endif
 
 inline void* GetPC(const struct ucontext_t& signal_ucontext) {
   RAW_LOG(ERROR, "GetPC is not yet implemented on Windows\n");
   return NULL;
 }
 #elif defined(__ANDROID__)
+namespace tcmalloc {
 typedef struct _Unwind_Context ucontext_t;
+}
 
-inline void* GetPC(const ucontext_t& signal_ucontext) {
+inline void* GetPC(const tcmalloc::ucontext_t& signal_ucontext) {
   // Bionic doesn't export ucontext, see
   // https://code.google.com/p/android/issues/detail?id=34784.
   return reinterpret_cast<void*>(_Unwind_GetIP(
-      const_cast<ucontext_t*>(&signal_ucontext)));
+      const_cast<tcmalloc::ucontext_t*>(&signal_ucontext)));
 }
 //
 // Normal cases.  If this doesn't compile, it's probably because
 // PC_FROM_UCONTEXT is the empty string.  You need to figure out
 // the right value for your system, and add it to the list in
 // configure.ac (or set it manually in your config.h).
 #else
 inline void* GetPC(const ucontext_t& signal_ucontext) {
   return (void*)signal_ucontext.PC_FROM_UCONTEXT;   // defined in config.h
 }
 
 #endif
 
 #endif  // BASE_GETPC_H_