Fix to use ucontext_t in unwind.h.

third_party/tcmalloc/chromium/src/profiler.cc

Index: third_party/tcmalloc/chromium/src/profiler.cc
diff --git a/third_party/tcmalloc/chromium/src/profiler.cc b/third_party/tcmalloc/chromium/src/profiler.cc
index eb6dc4281a5ec80b6e85cb0fcb63aef751c6429a..699a4a49d8810984c7e99cd0d849193ca83056b7 100644
--- a/third_party/tcmalloc/chromium/src/profiler.cc
+++ b/third_party/tcmalloc/chromium/src/profiler.cc
@@ -270,7 +270,11 @@ void CpuProfiler::prof_handler(int sig, siginfo_t*, void* signal_ucontext,
 
     // The top-most active routine doesn't show up as a normal
     // frame, but as the "pc" value in the signal handler context.
+#if defined(__ANDROID__)
+    stack[0] = GetPC(*reinterpret_cast<tcmalloc::ucontext_t*>(signal_ucontext));
+#else
     stack[0] = GetPC(*reinterpret_cast<ucontext_t*>(signal_ucontext));
+#endif
 
     // We skip the top two stack trace entries (this function and one
     // signal handler frame) since they are artifacts of profiling and