Make the StackFrameList::GetFrameAtIndex only fetch as many stack frames as needed to 
get the frame requested.
<rdar://problem/10943135>

llvm-svn: 151705
diff --git a/lldb/source/Plugins/Process/Utility/UnwindLLDB.h b/lldb/source/Plugins/Process/Utility/UnwindLLDB.h
index b9352b6..ff4030f 100644
--- a/lldb/source/Plugins/Process/Utility/UnwindLLDB.h
+++ b/lldb/source/Plugins/Process/Utility/UnwindLLDB.h
@@ -56,6 +56,7 @@
     DoClear()
     {
         m_frames.clear();
+        m_unwind_complete = false;
     }
 
     virtual uint32_t
@@ -98,6 +99,10 @@
 
     typedef SHARED_PTR(Cursor) CursorSP;
     std::vector<CursorSP> m_frames;
+    bool m_unwind_complete; // If this is true, we've enumerated all the frames in the stack, and m_frames.size() is the 
+                            // number of frames, etc.  Otherwise we've only gone as far as directly asked, and m_frames.size()
+                            // is how far we've currently gone.
+ 
 
     bool AddOneMoreFrame (ABI *abi);
     bool AddFirstFrame ();