Allow setting runtime-enabled features from a string.

Source/build/scripts/templates/RuntimeEnabledFeatures.h.tmpl

 {% from 'macros.tmpl' import license %}
 {{license()}}
 
 #ifndef RuntimeEnabledFeatures_h
 #define RuntimeEnabledFeatures_h
 
 #include "platform/PlatformExport.h"
+#include "wtf/Forward.h"
 
 namespace blink {
 
 // A class that stores static enablers for all experimental features.
 
 class PLATFORM_EXPORT RuntimeEnabledFeatures {
 public:
     {% for feature_set in feature_sets %}
     static void set{{feature_set|capitalize}}FeaturesEnabled(bool);
     {% endfor %}
 
+    static void setFeatureEnabledFromString(const WTF::String& name, bool isEnabled);
 
     {% for feature in features %}
     {% if feature.custom %}
     static bool {{feature.first_lowered_name}}Enabled();
     {% else %}
     {% if feature.condition %}
 #if ENABLE({{feature.condition}})
     {% endif %}
     static void set{{feature.name}}Enabled(bool isEnabled) { is{{feature.name}}Enabled = isEnabled; }
     static bool {{feature.first_lowered_name}}Enabled() { return {{feature.enabled_condition}}; }
@@ skipping 13 matching lines @@
     {% for feature in features if not feature.custom %}
     {% filter enable_conditional(feature.condition) %}
     static bool is{{feature.name}}Enabled;
     {% endfilter %}
     {% endfor %}
 };
 
 } // namespace blink
 
 #endif // RuntimeEnabledFeatures_h