Move pref and switch in preparation for metrics componentization

Code will shortly be componentized into the metrics component that uses
prefs::kMetricsReportingEnabled and switches::kForceFieldTrials. To enable that
componentization, this CL does the following:

- Moves prefs::kMetricsReportingEnabled into the metrics component.
- Moves switches:kForceFieldTrials from //content to //base to enable it to be
  used both by //content and by the metrics component.

BUG=508014

Review URL: https://codereview.chromium.org/1373823002

Cr-Commit-Position: refs/heads/master@{#351268}

1 files changed, 10 insertions, 0 deletions

diff --git a/base/base_switches.cc b/base/base_switches.cc
index 7f3be7f..76827b8 100644
--- a/base/base_switches.cc
+++ b/base/base_switches.cc
@@ -23,6 +23,16 @@ const char kEnableLowEndDeviceMode[]        = "enable-low-end-device-mode";
 // Force disabling of low-end device mode when set.
 const char kDisableLowEndDeviceMode[]       = "disable-low-end-device-mode";
 
+// This option can be used to force field trials when testing changes locally.
+// The argument is a list of name and value pairs, separated by slashes. If a
+// trial name is prefixed with an asterisk, that trial will start activated.
+// For example, the following argument defines two trials, with the second one
+// activated: "GoogleNow/Enable/*MaterialDesignNTP/Default/" This option can
+// also be used by the browser process to send the list of trials to a
+// non-browser process, using the same format. See
+// FieldTrialList::CreateTrialsFromString() in field_trial.h for details.
+const char kForceFieldTrials[]              = "force-fieldtrials";
+
 // Suppresses all error dialogs when present.
 const char kNoErrorDialogs[]                = "noerrdialogs";