Add working set base runtime library

Summary:
Adds the base runtime library for the working set tool.
Adds slowpath code for updating the shadow memory.

To be added in the future:
+ Scan memory and report the total size.
+ Take samples for intermediate values.

Reviewers: aizatsky

Subscribers: kubabrecka, vitalybuka, zhaoqin, kcc, eugenis, llvm-commits

Differential Revision: http://reviews.llvm.org/D20485

llvm-svn: 270650
diff --git a/compiler-rt/lib/esan/esan_interface_internal.h b/compiler-rt/lib/esan/esan_interface_internal.h
index 577c7e3..83e0433 100644
--- a/compiler-rt/lib/esan/esan_interface_internal.h
+++ b/compiler-rt/lib/esan/esan_interface_internal.h
@@ -28,6 +28,8 @@
 typedef enum Type : u32 {
   ESAN_None = 0,
   ESAN_CacheFrag,
+  ESAN_WorkingSet,
+  ESAN_Max,
 } ToolType;
 
 // This function should be called at the very beginning of the process,