Another temporary CHECK to help track down crash in IPC.

(Grasping at straws here.)

TBR=sievers@chromium.org, cpu@chromium.org
BUG=357915

Review URL: https://codereview.chromium.org/218513002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260408 0039d316-1c4b-4281-b951-d872f2087c98

ipc/ipc_message.cc

@@ -84,6 +84,8 @@ void Message::InitLoggingVariables() {
 
 Message& Message::operator=(const Message& other) {
   *static_cast<Pickle*>(this) = other;
+  // TODO(vtl): Remove once bug resolved.
+  CHECK(header()) << "crbug.com/357915";
 #if defined(OS_POSIX)
   file_descriptor_set_ = other.file_descriptor_set_;
 #endif