Field Trials choices can now be forced from a command line argument, and yet still behave as if a coin was tossed, except the coin is tricked :-).

To do this, we needed to change the usage from a regular constructor (which is not private) to a static CreateInstance method (which is why there is a bunch of TBR'd owners, those changes were trivial to existing users of FieldTrials).

OWNERs of trivially changed files:
TBR=sky,jamesr,cpu,joi,

BUG=119726
TEST=base_unittests.exe --gtest_filter=FieldTrialTest.*
You can also find an active field trial name and force it to a given group by passing the following command line argument "--force-fieldtest=<trial_name>/<default_group_name>/<group_name>/"

Review URL: http://codereview.chromium.org/9705074

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@131948 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 12 insertions, 14 deletions

diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index d62cada..e38a37f 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -632,7 +632,7 @@ void RenderProcessHostImpl::AppendRendererCommandLine(
   std::string field_trial_states;
   base::FieldTrialList::StatesToString(&field_trial_states);
   if (!field_trial_states.empty()) {
-    command_line->AppendSwitchASCII(switches::kForceFieldTestNameAndValue,
+    command_line->AppendSwitchASCII(switches::kForceFieldTrials,
                                     field_trial_states);
   }
 
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 2819e1d..c660c57 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -366,17 +366,15 @@ const char kExtraPluginDir[]                = "extra-plugin-dir";
 // the base layer even when compositing is not strictly required.
 const char kForceCompositingMode[]          = "force-compositing-mode";
 
-// Some field tests may rendomized in the browser, and the randomly selected
-// outcome needs to be propagated to the renderer.  For instance, this is used
+// Some field trials may be randomized in the browser, and the randomly selected
+// outcome needs to be propagated to the renderer. For instance, this is used
 // to modify histograms recorded in the renderer, or to get the renderer to
 // also set of its state (initialize, or not initialize components) to match the
-// experiment(s).
-// The argument is a string-ized list of experiment names, and the associated
-// value that was randomly selected.  In the recent implementetaion, the
-// persistent representation generated by field_trial.cc and later decoded, is a
-// list of name and value pairs, separated by slashes. See field trial.cc for
-// current details.
-const char kForceFieldTestNameAndValue[]    = "force-fieldtest";
+// experiment(s). The option is also useful for forcing field trials when
+// testing changes locally. The argument is a list of name and value pairs,
+// separated by slashes. See FieldTrialList::CreateTrialsFromString() in
+// field_trial.h for details.
+const char kForceFieldTrials[]              = "force-fieldtrials";
 
 // Force renderer accessibility to be on instead of enabling it on demand when
 // a screen reader is detected. The disable-renderer-accessibility switch
diff --git a/content/public/common/content_switches.h b/content/public/common/content_switches.h
index d63df83..fb1bff4 100644
--- a/content/public/common/content_switches.h
+++ b/content/public/common/content_switches.h
@@ -117,7 +117,7 @@ CONTENT_EXPORT extern const char kDisableWebIntents[];
 CONTENT_EXPORT extern const char kExperimentalLocationFeatures[];
 extern const char kExtraPluginDir[];
 CONTENT_EXPORT extern const char kForceCompositingMode[];
-extern const char kForceFieldTestNameAndValue[];
+extern const char kForceFieldTrials[];
 CONTENT_EXPORT extern const char kForceRendererAccessibility[];
 extern const char kGpuLauncher[];
 CONTENT_EXPORT extern const char kGpuProcess[];
diff --git a/content/renderer/renderer_main.cc b/content/renderer/renderer_main.cc
index becc623..24354fe 100644
--- a/content/renderer/renderer_main.cc
+++ b/content/renderer/renderer_main.cc
@@ -236,10 +236,10 @@ int RendererMain(const content::MainFunctionParams& parameters) {
   // one-time randomized trials; they should be created in the browser process.
   base::FieldTrialList field_trial(EmptyString());
   // Ensure any field trials in browser are reflected into renderer.
-  if (parsed_command_line.HasSwitch(switches::kForceFieldTestNameAndValue)) {
+  if (parsed_command_line.HasSwitch(switches::kForceFieldTrials)) {
     std::string persistent = parsed_command_line.GetSwitchValueASCII(
-        switches::kForceFieldTestNameAndValue);
-    bool ret = field_trial.CreateTrialsInChildProcess(persistent);
+        switches::kForceFieldTrials);
+    bool ret = base::FieldTrialList::CreateTrialsFromString(persistent);
     DCHECK(ret);
   }