[PATCH] Fixes in LargeMmapAllocator::GetBlockBegin().

[Kostya Serebryany]

================
Comment at: lib/sanitizer_common/sanitizer_allocator.h:1019
@@ -1018,1 +1018,3 @@
+      return 0;
+    if (h->map_beg + page_size_ > p)
       return 0;
----------------
you've changed two checks but added one test
did you run the asan tests? 


http://llvm-reviews.chandlerc.com/D624