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/Target/ABI.cpp b/source/Target/ABI.cpp
index 0ac91da..069a132 100644
--- a/source/Target/ABI.cpp
+++ b/source/Target/ABI.cpp
@@ -105,8 +105,8 @@
 
 ValueObjectSP
 ABI::GetReturnValueObject (Thread &thread,
-                          ClangASTType &ast_type,
-                          bool persistent) const
+                           ClangASTType &ast_type,
+                           bool persistent) const
 {
     if (!ast_type.IsValid())
         return ValueObjectSP();
@@ -123,7 +123,7 @@
     
     if (persistent)
     {
-        ClangPersistentVariables& persistent_variables = thread.GetProcess().GetTarget().GetPersistentVariables();
+        ClangPersistentVariables& persistent_variables = thread.CalculateTarget()->GetPersistentVariables();
         ConstString persistent_variable_name (persistent_variables.GetNextPersistentVariableName());
 
         lldb::ValueObjectSP const_valobj_sp;