Clean up UMA 3g experiment and unify metrics enabled pref for Android

chrome/common/pref_names.h

 // Copyright (c) 2012 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.
 
 // Constants for the names of various preferences, for easier changing.
 
 #ifndef CHROME_COMMON_PREF_NAMES_H_
 #define CHROME_COMMON_PREF_NAMES_H_
 
 #include <stddef.h>
@@ skipping 428 matching lines @@
 extern const char kGLVersionString[];
 
 #if defined(OS_ANDROID)
 extern const char kGLExtensionsString[];
 extern const char kGpuDriverInfoMaxSamples[];
 extern const char kGpuDriverInfoResetNotificationStrategy[];
 extern const char kGpuDriverInfoShaderVersion[];
 extern const char kGpuDriverInfoBuildFingerPrint[];
 #endif
 
-// Android has it's own metric / crash reporting implemented in Android
-// Java code so kMetricsReportingEnabled doesn't make sense. We use this
-// to inform crashes_ui that we have enabled crash reporting.
+// Deprecated preference for metric / crash reporting on Android. Use
+// kMetricsReportingEnabled instead.
 #if BUILDFLAG(ANDROID_JAVA_UI)
 extern const char kCrashReportingEnabled[];
 #endif
 
 extern const char kDeviceOpenNetworkConfiguration[];
 
 extern const char kProfileLastUsed[];
 extern const char kProfilesLastActive[];
 extern const char kProfilesNumCreated[];
 extern const char kProfileInfoCache[];
@@ skipping 365 matching lines @@
 #endif
 
 extern const char kOriginTrialPublicKey[];
 extern const char kOriginTrialDisabledFeatures[];
 
 extern const char kComponentUpdatesEnabled[];
 
 }  // namespace prefs
 
 #endif  // CHROME_COMMON_PREF_NAMES_H_