Add a mechanism to force parameters of a group to a specific value.

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index f9b5801177ce6e5ce67172934ce1a224e3b09237..826cf3733d40c9434799a8baa189962043fb1b19 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -529,6 +529,15 @@ const char kExtraPluginDir[]                = "extra-plugin-dir";
 // FieldTrialList::CreateTrialsFromString() in field_trial.h for details.
 const char kForceFieldTrials[]              = "force-fieldtrials";
 
+// This option can be used to force parameters of field trials when testing
+// changes locally. The argument is a list of key/value pairs. Where the key
+// is defined by the format TrialName.GroupName.ParamName. The following
+// forces "id" to be "foo" for the "Enabled" group of the "EnhancedBookmarks"
+// trial: "EnhancedBookmarks.Enabled.id/foo/"
+// variations::AssociateParamsFromString() in variations_associated_data.h for
+// details.
+const char kForceFieldTrialParams[]        = "force-fieldtrial-params";
+
 // Always use the Skia GPU backend for drawing layer tiles. Only valid with GPU
 // accelerated compositing + impl-side painting. Overrides the
 // kEnableGpuRasterization flag.