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/Breakpoint/StoppointCallbackContext.cpp b/source/Breakpoint/StoppointCallbackContext.cpp
index da4d9e3..2266c3e 100644
--- a/source/Breakpoint/StoppointCallbackContext.cpp
+++ b/source/Breakpoint/StoppointCallbackContext.cpp
@@ -18,13 +18,14 @@
 
 StoppointCallbackContext::StoppointCallbackContext() :
     event (NULL),
-    exe_ctx()
+    exe_ctx_ref (),
+    is_synchronous (false)
 {
 }
 
-StoppointCallbackContext::StoppointCallbackContext(Event *e, Process* p, Thread *t, StackFrame *f, bool synchronously) :
+StoppointCallbackContext::StoppointCallbackContext(Event *e, const ExecutionContext &exe_ctx, bool synchronously) :
     event (e),
-    exe_ctx (p, t, f),
+    exe_ctx_ref (exe_ctx),
     is_synchronous(synchronously)
 {
 }
@@ -33,6 +34,6 @@
 StoppointCallbackContext::Clear()
 {
     event = NULL;
-    exe_ctx.Clear();
+    exe_ctx_ref.Clear();
     is_synchronous = false;
 }