meminfo: Add support to track working set with idle page tracking.

Also adds a tool to make use of this if it exists call 'wsstop'

Bug: 111694435
Test: wsstop -d 3 -n 100 1

Change-Id: I50415f0bdc09c09b5b414cf0e4fff8f2907c5823
Signed-off-by: Sandeep Patil <sspatil@google.com>
diff --git a/libmeminfo/tools/Android.bp b/libmeminfo/tools/Android.bp
index 24054c6..2e89c41 100644
--- a/libmeminfo/tools/Android.bp
+++ b/libmeminfo/tools/Android.bp
@@ -67,3 +67,17 @@
         "libmeminfo",
     ],
 }
+
+cc_binary {
+    name: "wsstop",
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
+    srcs: ["wsstop.cpp"],
+    shared_libs: [
+        "libbase",
+        "liblog",
+        "libmeminfo",
+    ],
+}