Record device scale factor in the metrics log

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 b34456f9fff95e8a9e1544fc5c82e6022c464637..82ed3aeb55a470cd13315e0020c98759cb8ac7f7 100644
--- a/chrome/common/metrics/proto/system_profile.proto
+++ b/chrome/common/metrics/proto/system_profile.proto
@@ -11,7 +11,7 @@ option optimize_for = LITE_RUNTIME;
 
 package metrics;
 
-// Next tag: 12
+// Next tag: 13
 message SystemProfileProto {
   // The time when the client was compiled/linked, in seconds since the epoch.
   optional int64 build_timestamp = 1;
@@ -98,6 +98,9 @@ message SystemProfileProto {
     optional int32 primary_screen_width = 6;
     optional int32 primary_screen_height = 7;
 
+    // The device scale factor of the primary screen.
+    optional float primary_screen_scale_factor = 12;
+
     // Information on the GPU
     message Graphics {
       // The GPU manufacturer's vendor id.