Revert of Revert of MSan: check data is initialized when serializing with base::Pickle.

base/pickle.cc

Index: base/pickle.cc
diff --git a/base/pickle.cc b/base/pickle.cc
index d461f413dfd2e68a6e97c9f15d5d97dc68faacb3..b2490aa8ada0782ac568ab10b95f700ee313874c 100644
--- a/base/pickle.cc
+++ b/base/pickle.cc
@@ -353,6 +353,7 @@
 inline void Pickle::WriteBytesCommon(const void* data, size_t length) {
   DCHECK_NE(kCapacityReadOnly, capacity_after_header_)
       << "oops: pickle is readonly";
+  MSAN_CHECK_MEM_IS_INITIALIZED(data, length);
   size_t data_len = AlignInt(length, sizeof(uint32));
   DCHECK_GE(data_len, length);
 #ifdef ARCH_CPU_64_BITS