Add missing schemes to RecordMainFrameNavigation

components/navigation_metrics/navigation_metrics.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/navigation_metrics/navigation_metrics.h"
 
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "url/gurl.h"
 
 namespace {
 
-// This enum is used in building the histogram. So, this is append only,
-// any new scheme should be added at the end, before SCHEME_MAX
+// These values are written to logs. New enum values can be added, but existing
+// enums must never be renumbered or deleted and reused. Any new scheme should
+// be added at the end, before SCHEME_MAX.
 enum Scheme {
-  SCHEME_UNKNOWN,
-  SCHEME_HTTP,
-  SCHEME_HTTPS,
-  SCHEME_FILE,
-  SCHEME_FTP,
-  SCHEME_DATA,
-  SCHEME_JAVASCRIPT,
-  SCHEME_ABOUT,
-  SCHEME_CHROME,
-  SCHEME_BLOB,
-  SCHEME_FILESYSTEM,
+  SCHEME_UNKNOWN = 0,
+  SCHEME_HTTP = 1,
+  SCHEME_HTTPS = 2,
+  SCHEME_FILE = 3,
+  SCHEME_FTP = 4,
+  SCHEME_DATA = 5,
+  SCHEME_JAVASCRIPT = 6,
+  SCHEME_ABOUT = 7,
+  SCHEME_CHROME = 8,
+  SCHEME_BLOB = 9,
+  SCHEME_FILESYSTEM = 10,
+  SCHEME_CHROME_NATIVE = 11,
+  SCHEME_CHROME_SEARCH = 12,
+  SCHEME_CHROME_DISTILLER = 13,
+  SCHEME_CHROME_DEVTOOLS = 14,
+  SCHEME_CHROME_EXTENSION = 15,
+  SCHEME_VIEW_SOURCE = 16,
+  SCHEME_EXTERNALFILE = 17,
   SCHEME_MAX,
 };
 
 const char* const kSchemeNames[] = {
     "unknown",
     url::kHttpScheme,
     url::kHttpsScheme,
     url::kFileScheme,
     url::kFtpScheme,
     url::kDataScheme,
     url::kJavaScriptScheme,
     url::kAboutScheme,
     "chrome",
     url::kBlobScheme,
     url::kFileSystemScheme,
+    "chrome-native",

[Mark P, 2017/06/28 17:28:42]

nit: you're using raw strings here.  Aren't many of these defined as named
constants in various places?

[elawrence, 2017/06/28 20:19:59]

Yes. Unfortunately, those "various places" are mostly not usable from this
component. Most of the constants are defined either in /src/chrome, or
defined/redefined in src/content; the latter we cannot depend upon because
navigation_metrics isn't a layered component.

I've switched to use the constant for chrome-distiller, as that one is defined
in a header we can use here.

+    "chrome-search",
+    "chrome-distiller",
+    "chrome-devtools",
+    "chrome-extension",
+    "view-source",
+    "externalfile",
     "max",
 };
 
 static_assert(arraysize(kSchemeNames) == SCHEME_MAX + 1,
               "kSchemeNames should have SCHEME_MAX + 1 elements");
 
 }  // namespace
 
 namespace navigation_metrics {
 
@@ skipping 18 matching lines @@
     UMA_HISTOGRAM_ENUMERATION("Navigation.MainFrameSchemeOTR", scheme,
                               SCHEME_MAX);
     if (!is_same_document) {
       UMA_HISTOGRAM_ENUMERATION("Navigation.MainFrameSchemeDifferentPageOTR",
                                 scheme, SCHEME_MAX);
     }
   }
 }
 
 }  // namespace navigation_metrics