[ImportantSites] Adding usage metrics.

chrome/browser/android/preferences/pref_service_bridge.cc

 // Copyright 2014 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 "chrome/browser/android/preferences/pref_service_bridge.h"
 
 #include <jni.h>
 #include <stddef.h>
 
 #include <memory>
@@ skipping 53 matching lines @@
 
 using base::android::AttachCurrentThread;
 using base::android::CheckException;
 using base::android::ConvertJavaStringToUTF8;
 using base::android::ConvertUTF8ToJavaString;
 using base::android::ScopedJavaLocalRef;
 using base::android::ScopedJavaGlobalRef;
 using content::BrowserThread;
 
 namespace {
+
+// This should never change, as it's used for UMA metrics.

[Mark P, 2016/06/30 05:29:09]

You don't need this warning.  The problem I envisioned had to do with it
changing during a single session.  If it changes between sessions (say, during a
binary update), that's fine.

[dmurph, 2016/06/30 20:16:29]

Ah, ok.

 const size_t kMaxImportantSites = 5;
 
 Profile* GetOriginalProfile() {
   return ProfileManager::GetActiveUserProfile()->GetOriginalProfile();
 }
 
 bool GetBooleanForContentSetting(ContentSettingsType type) {
   HostContentSettingsMap* content_settings =
       HostContentSettingsMapFactory::GetForProfile(GetOriginalProfile());
   switch (content_settings->GetDefaultContentSetting(type, NULL)) {
@@ skipping 592 matching lines @@
   std::transform(example_origins.begin(), example_origins.end(),
                  important_domains.begin(),
                  [](const GURL& origin) { return origin.spec(); });
   ScopedJavaLocalRef<jobjectArray> java_origins =
       base::android::ToJavaArrayOfStrings(env, important_domains);
 
   Java_ImportantSitesCallback_onImportantRegisterableDomainsReady(
       env, java_callback.obj(), java_domains.obj(), java_origins.obj());
 }
 
+// This should never return a different constant, as it's used for UMA metrics.

[Mark P, 2016/06/30 05:29:09]

more correct:
// This value should no change during a sessions, as it's used for UMA metrics.

[dmurph, 2016/06/30 20:16:29]

Done.

 static jint GetMaxImportantSites(JNIEnv* env,
                                  const JavaParamRef<jclass>& clazz) {
   return kMaxImportantSites;
 }
 
 static void MarkOriginAsImportantForTesting(
     JNIEnv* env,
     const JavaParamRef<jclass>& clazz,
     const JavaParamRef<jstring>& jorigin) {
   GURL origin(base::android::ConvertJavaStringToUTF8(jorigin));
@@ skipping 488 matching lines @@
 
   return ConvertJavaStringToUTF8(android_permission);
 }
 
 static void SetSupervisedUserId(JNIEnv* env,
                                 const JavaParamRef<jobject>& obj,
                                 const JavaParamRef<jstring>& pref) {
   GetPrefService()->SetString(prefs::kSupervisedUserId,
                               ConvertJavaStringToUTF8(env, pref));
 }