Advertise a minimum alignment for SharedMemory::Map().

base/shared_memory_win.cc

Index: base/shared_memory_win.cc
diff --git a/base/shared_memory_win.cc b/base/shared_memory_win.cc
index 042eb8bdac065c5b1d1911faeee66c5a1e2f1569..a4f86cbc15de70e51389caa21ad0458f9cff9b7e 100644
--- a/base/shared_memory_win.cc
+++ b/base/shared_memory_win.cc
@@ -136,6 +136,8 @@ bool SharedMemory::Map(uint32 bytes) {
   memory_ = MapViewOfFile(mapped_file_,
       read_only_ ? FILE_MAP_READ : FILE_MAP_ALL_ACCESS, 0, 0, bytes);
   if (memory_ != NULL) {
+    DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
+        (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
     return true;
   }
   return false;