Include external touchscreen vid/pid in UMA hardware profile

chrome/common/metrics/proto/system_profile.proto

Index: chrome/common/metrics/proto/system_profile.proto
diff --git a/chrome/common/metrics/proto/system_profile.proto b/chrome/common/metrics/proto/system_profile.proto
index abeea2bb0f269a0cffb5d528b80a890ce25bf025..6be718e15d9bf404a6975e2fe5cc31c8e4cd26de 100644
--- a/chrome/common/metrics/proto/system_profile.proto
+++ b/chrome/common/metrics/proto/system_profile.proto
@@ -83,7 +83,7 @@ message SystemProfileProto {
   }
   optional OS os = 5;
 
-  // Next tag for Hardware: 14
+  // Next tag for Hardware: 15
   // Information on the user's hardware.
   message Hardware {
     // The CPU architecture (x86, PowerPC, x86_64, ...)
@@ -219,6 +219,13 @@ message SystemProfileProto {
       repeated PairedDevice paired_device = 3;
     }
     optional Bluetooth bluetooth = 11;
+
+    // vids and pids of external touchscreens.
+    message TouchScreen {
+      optional uint32 vendor_id = 1;
+      optional uint32 product_id = 2;
+    }
+    repeated TouchScreen external_touchscreen = 14;
   }
   optional Hardware hardware = 6;