Roll UMA & Variations protos

Update chromium protos to match internal ones.

Bug: 1025781
Change-Id: I6c7c39d21d574e2e5f42cf51026a11e876946309
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2005188Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732519}

third_party/metrics_proto/README.chromium

 Name: Metrics Protos
 Short Name: metrics_proto
 URL: This is the canonical public repository
-Version: 283899508
-Date: 2019/12/05 UTC
+Version: 290085301
+Date: 2020/01/16 UTC
 License: BSD
 Security Critical: Yes
 

third_party/metrics_proto/chrome_user_metrics_extension.proto

@@ -39,6 +39,9 @@ message ChromeUserMetricsExtension {
 
     // Cast receivers, e.g. Chromecast
     CAST = 35;
+
+    // UMA metrics from Android WebLayer.
+    ANDROID_WEBLAYER = 56;
   }
   // The product corresponding to this log. The field type is int32 instead of
   // Product so that downstream users of the Chromium metrics component can

third_party/metrics_proto/system_profile.proto

@@ -15,7 +15,7 @@ import "extension_install.proto";
 
 // Stores information about the user's brower and system configuration.
 // The system configuration fields are recorded once per client session.
-// Next tag: 31
+// Next tag: 33
 message SystemProfileProto {
   // The time when the client was compiled/linked, in seconds since the epoch.
   optional int64 build_timestamp = 1;
@@ -74,6 +74,17 @@ message SystemProfileProto {
   // For privacy, this is rounded to the nearest hour.
   optional int64 install_date = 16;
 
+  // The non-identifying low entropy source value. This value seeds the
+  // pseudorandom generator which picks experimental groups.
+  optional int32 low_entropy_source = 31;
+
+  // The old low entropy value. This value is thought to be biased in the wild,
+  // and is no longer used for experiments requiring low entropy. Clients which
+  // already have an "old" value continue incorporating it into the high entropy
+  // source, to avoid changing those group assignments. New clients only have
+  // the new source.
+  optional int32 old_low_entropy_source = 32;
+
   // The user's selected application locale, i.e. the user interface language.
   // The locale includes a language code and, possibly, also a country code,
   // e.g. "en-US".