Histogram the scheme of an origin on the 1st navigation to it.

components/navigation_metrics/navigation_metrics.cc

Index: components/navigation_metrics/navigation_metrics.cc
diff --git a/components/navigation_metrics/navigation_metrics.cc b/components/navigation_metrics/navigation_metrics.cc
index e0d61c769f7b6a5daa6c876951b4870d02babf58..69a2403aa467e131f815b530ecba85fba4951426 100644
--- a/components/navigation_metrics/navigation_metrics.cc
+++ b/components/navigation_metrics/navigation_metrics.cc
@@ -47,7 +47,9 @@ static_assert(arraysize(kSchemeNames) == SCHEME_MAX + 1,
 
 namespace navigation_metrics {
 
-void RecordMainFrameNavigation(const GURL& url, bool is_in_page) {
+void RecordMainFrameNavigation(const GURL& url,
+                               bool is_in_page,
+                               bool is_off_the_record) {
   Scheme scheme = SCHEME_UNKNOWN;
   for (int i = 1; i < SCHEME_MAX; ++i) {
     if (url.SchemeIs(kSchemeNames[i])) {
@@ -55,11 +57,16 @@ void RecordMainFrameNavigation(const GURL& url, bool is_in_page) {
       break;
     }
   }
-  UMA_HISTOGRAM_ENUMERATION("Navigation.MainFrameScheme", scheme, SCHEME_MAX);
-  if (!is_in_page) {
-    UMA_HISTOGRAM_ENUMERATION(
-        "Navigation.MainFrameSchemeDifferentPage", scheme, SCHEME_MAX);
+
+  const char* enumeration_mfs = "Navigation.MainFrameScheme";
+  const char* enumeration_mfs_dp = "Navigation.MainFrameSchemeDifferentPage";
+  if (is_off_the_record) {
+    enumeration_mfs = "Navigation.IncognitoMainFrameScheme";
+    enumeration_mfs_dp = "Navigation.IncognitoMainFrameSchemeDifferentPage";
   }
+  UMA_HISTOGRAM_ENUMERATION(enumeration_mfs, scheme, SCHEME_MAX);

[felt, 2016/04/01 00:01:59]

Does this actually work? I thought the histogram macros require string literals
or else they barfed, or has that been fixed?

[palmer, 2016/04/05 23:42:18]

It compiles and runs, but the comments about lazy initialization in
base/metrics/histogram_macros.h have me wondering, now that you mention it. I've
changed it to use literals.

+  if (!is_in_page)
+    UMA_HISTOGRAM_ENUMERATION(enumeration_mfs_dp, scheme, SCHEME_MAX);
 }
 
 }  // namespace navigation_metrics