Add support for MojoChannel field trial

content/public/common/mojo_channel_switches.cc

 // Copyright 2015 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 "content/public/common/mojo_channel_switches.h"
 
 #include "base/command_line.h"
+#include "base/metrics/field_trial.h"
 #include "ipc/mojo/ipc_channel_mojo.h"
 #include "mojo/common/common_type_converters.h"
 
 namespace switches {
 
-// Replaces renderer-browser IPC channel with ChnanelMojo.
-// TODO(morrita): Now ChannelMojo for the renderer is on by default.
-// Remove this once the change sticks.
-const char kEnableRendererMojoChannel[] =
-    "enable-renderer-mojo-channel";
-
-// Disable ChannelMojo usage regardless of the platform or the process type.
-const char kDisableMojoChannel[] = "disable-mojo-channel";
+// Enable ChannelMojo on any supported platform.
+const char kEnableMojoChannel[] = "enable-mojo-channel";
 
 // The token to use to construct the message pipe on which to layer ChannelMojo.
 const char kMojoChannelToken[] = "mojo-channel-token";
 
 }  // namespace switches
 
+namespace {
+
+const char kMojoChannelExperimentName[] = "MojoChannel";
+
+}  // namespace
+
 namespace content {
 
 bool ShouldUseMojoChannel() {
-  const base::CommandLine& command_line =
-      *base::CommandLine::ForCurrentProcess();
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableMojoChannel))
+    return true;
 
-  if (command_line.HasSwitch(switches::kDisableMojoChannel))
-    return false;
-  if (command_line.HasSwitch(switches::kEnableRendererMojoChannel))
+  const std::string group =
+      base::FieldTrialList::FindFullName(kMojoChannelExperimentName);

[Will Harris, 2016/04/15 16:59:54]

the query to FindFullName should always take place, otherwise some clients will
not be placed in any experiment group, and your data will be wrong.

+  if (group == "Enabled")
     return true;
-  return IPC::ChannelMojo::ShouldBeUsed();
+
+  return false;
 }
 
 }  // namespace content