Support loading trial tokens from HTTP headers.

third_party/WebKit/Source/build/scripts/templates/OriginTrials.h.tmpl

 {% from 'macros.tmpl' import license %}
 {{license()}}
 
 #ifndef OriginTrials_h
 #define OriginTrials_h
 
 #include "core/CoreExport.h"
 #include "core/origin_trials/OriginTrialsBase.h"
 #include "platform/Supplementable.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class ExecutionContext;
 class OriginTrialContext;
 
 // A class that stores dynamic tests for experimental features which can be
 // enabled through the experimental framework via API keys.
 
 class CORE_EXPORT OriginTrials final : public OriginTrialsBase, public WillBeHeapSupplement<ExecutionContext> {
 WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(OriginTrials)
 public:
     static const char* supplementName();
     static OriginTrials* from(ExecutionContext*);
+    static void setTrialTokensFromHeader(ExecutionContext*, const String& headerValue);
 
     {% for feature in features %}
     {% if feature.origin_trial_feature_name %}
 
     static bool {{feature.first_lowered_name}}Enabled(ExecutionContext*, String& errorMessage);
     static bool {{feature.first_lowered_name}}Enabled(ExecutionContext*);
     {% endif %}
     {% endfor %}
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit OriginTrials(ExecutionContext*);
 
     {% for feature in features %}
     {% if feature.origin_trial_feature_name %}
     bool {{feature.first_lowered_name}}EnabledImpl(String* errorMessage);
     {% endif %}
     {% endfor %}
 };
 
 } // namespace blink
 
 #endif // OriginTrials_h