Thread hardening part 3. Now lldb_private::Thread objects have std::weak_ptr
objects for the backlink to the lldb_private::Process. The issues we were
running into before was someone was holding onto a shared pointer to a 
lldb_private::Thread for too long, and the lldb_private::Process parent object
would get destroyed and the lldb_private::Thread had a "Process &m_process"
member which would just treat whatever memory that used to be a Process as a
valid Process. This was mostly happening for lldb_private::StackFrame objects
that had a member like "Thread &m_thread". So this completes the internal
strong/weak changes.

Documented the ExecutionContext and ExecutionContextRef classes so that our
LLDB developers can understand when and where to use ExecutionContext and 
ExecutionContextRef objects.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@151009 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp b/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
index ab872f8..3b45691 100644
--- a/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
+++ b/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
@@ -312,7 +312,7 @@
         lldb::tid_t tid = cpu_mask_bit;
         ThreadSP thread_sp (old_thread_list.FindThreadByID (tid, false));
         if (!thread_sp)
-            thread_sp.reset(new ThreadKDP (*this, tid));
+            thread_sp.reset(new ThreadKDP (shared_from_this(), tid));
         new_thread_list.AddThread(thread_sp);
     }
     return new_thread_list.GetSize(false);