Revert 260408 "Another temporary CHECK to help track down crash ..."

> 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

TBR=viettrungluu@chromium.org

Review URL: https://codereview.chromium.org/218573002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@260418 0039d316-1c4b-4281-b951-d872f2087c98

ipc/ipc_message.cc

@@ -84,8 +84,6 @@ 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