Add histogram for SameSite attribute of a SameParty cookie

This adds a histogram to log the SameSite attribute on every attempt to
create a SameParty cookie.

Bug: 1142606
Change-Id: Ic63373aea2916ea3d9c9c666880535b05a3031ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2510492Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822820}

net/cookies/canonical_cookie.cc

@@ -414,7 +414,8 @@ std::unique_ptr<CanonicalCookie> CanonicalCookie::Create(
 
   CookieSameSiteString samesite_string = CookieSameSiteString::kUnspecified;
   CookieSameSite samesite = parsed_cookie.SameSite(&samesite_string);
-  RecordCookieSameSiteAttributeValueHistogram(samesite_string);
+  RecordCookieSameSiteAttributeValueHistogram(samesite_string,
+                                              parsed_cookie.IsSameParty());
   CookieSourceScheme source_scheme = url.SchemeIsCryptographic()
                                          ? CookieSourceScheme::kSecure
                                          : CookieSourceScheme::kNonSecure;

net/cookies/cookie_constants.cc

@@ -4,6 +4,7 @@
 
 #include "net/cookies/cookie_constants.h"
 
+#include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/notreached.h"
 #include "base/strings/string_util.h"
@@ -97,8 +98,13 @@ CookieSameSite StringToCookieSameSite(const std::string& same_site,
   return samesite;
 }
 
-void RecordCookieSameSiteAttributeValueHistogram(CookieSameSiteString value) {
+void RecordCookieSameSiteAttributeValueHistogram(CookieSameSiteString value,
+                                                 bool is_cookie_same_party) {
   UMA_HISTOGRAM_ENUMERATION("Cookie.SameSiteAttributeValue", value);
+  if (is_cookie_same_party) {
+    base::UmaHistogramEnumeration(
+        "Cookie.SamePartyCookieSameSiteAttributeValue", value);
+  }
 }
 
 }  // namespace net

net/cookies/cookie_constants.h

@@ -116,7 +116,8 @@ StringToCookieSameSite(const std::string& same_site,
                        CookieSameSiteString* samesite_string = nullptr);
 
 NET_EXPORT void RecordCookieSameSiteAttributeValueHistogram(
-    CookieSameSiteString value);
+    CookieSameSiteString value,
+    bool is_cookie_same_party = false);
 
 }  // namespace net
 

tools/metrics/histograms/histograms_xml/cookie/histograms.xml

@@ -236,8 +236,19 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="Cookie.SamePartyCookieSameSiteAttributeValue"
+    enum="CookieSameSiteString" expires_after="2021-11-01">
+  <owner>chlily@chromium.org</owner>
+  <owner>kaustubhag@chromium.org</owner>
+  <summary>
+    The value of a SameParty cookie's SameSite attribute, if any. This is logged
+    once per attempt to create a SameParty cookie, regardless of success, upon
+    parsing of the SameSite attribute from a string.
+  </summary>
+</histogram>
+
 <histogram name="Cookie.SameSiteAttributeValue" enum="CookieSameSiteString"
-    expires_after="M90">
+    expires_after="2021-11-01">
   <owner>chlily@chromium.org</owner>
   <owner>bingler@chromium.org</owner>
   <summary>