Add an about:flag for enabling a reader mode toolbar icon.

chrome/browser/android/chrome_startup_flags.cc

Index: chrome/browser/android/chrome_startup_flags.cc
diff --git a/chrome/browser/android/chrome_startup_flags.cc b/chrome/browser/android/chrome_startup_flags.cc
index 6c4a54ebea29dc4eb1983f6af79f6db95899341d..d5d200f0a370b8787d0479457af4cffe1fbafeb3 100644
--- a/chrome/browser/android/chrome_startup_flags.cc
+++ b/chrome/browser/android/chrome_startup_flags.cc
@@ -47,11 +47,6 @@ void SetChromeSpecificCommandLineFlags() {
   if (base::SysInfo::IsLowEndDevice())
     SetCommandLineSwitchASCII(switches::kDisableSyncTypes, "Favicon Images");
 
-  // Enable DOM Distiller on local builds, canary and dev-channel.
-  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
-  if (channel == chrome::VersionInfo::CHANNEL_UNKNOWN ||
-      channel == chrome::VersionInfo::CHANNEL_CANARY ||
-      channel == chrome::VersionInfo::CHANNEL_DEV) {
-    SetCommandLineSwitch(switches::kEnableDomDistiller);
-  }
+  // Enable DOM Distiller backend.
+  SetCommandLineSwitch(switches::kEnableDomDistiller);
 }