Remove NetPrefObserver class and two prefs that do not do anything.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index c0ee2d30d80892413542531cf4edf3aecb56fa21..d85b23271e84d53dd18dd2b365a8068c6bcb43e7 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -433,10 +433,6 @@ const char kDnsPrefetchingStartupList[] = "dns_prefetching.startup_list";
 const char kDnsPrefetchingHostReferralList[] =
     "dns_prefetching.host_referral_list";
 
-// Disables the SPDY/3.1 protocol.
-// DEPRECATED: SPDY/3.1 is not supported any more.
-const char kDisableSpdy[] = "spdy.disabled";
-
 // Prefs for persisting HttpServerProperties.
 const char kHttpServerProperties[] = "net.http_server_properties";
 
@@ -451,15 +447,6 @@ const char kLastPolicyCheckTime[] = "policy.last_policy_check_time";
 const char kInstantUIZeroSuggestUrlPrefix[] =
     "instant_ui.zero_suggest_url_prefix";
 
-// A boolean pref set to true if prediction of network actions is allowed.
-// Actions include DNS prefetching, TCP and SSL preconnection, prerendering
-// of web pages, and resource prefetching.
-// NOTE: The "dns_prefetching.enabled" value is used so that historical user
-// preferences are not lost.
-// TODO(bnc): Remove kNetworkPredictionEnabled once kNetworkPredictionOptions
-// is functioning as per crbug.com/334602.

[gab, 2016/07/22 16:44:33]

Should crbug.com/334602 be listed in CL description?

[Bence, 2016/07/23 00:16:42]

Done.

-const char kNetworkPredictionEnabled[] = "dns_prefetching.enabled";
-
 // A preference of enum chrome_browser_net::NetworkPredictionOptions shows
 // if prediction of network actions is allowed, depending on network type.
 // Actions include DNS prefetching, TCP and SSL preconnection, prerendering