Support loading trial tokens from HTTP headers.

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

 {% from 'macros.tmpl' import license %}
 {{license()}}
 
 #include "core/origin_trials/OriginTrials.h"
 
 #include "core/dom/ExecutionContext.h"
 #include "platform/RuntimeEnabledFeatures.h"
 
 namespace blink {
 
@@ skipping 10 matching lines @@
     if (!originTrials) {
         originTrials = new OriginTrials(host);
         WillBeHeapSupplement<ExecutionContext>::provideTo(*host, supplementName(), adoptPtrWillBeNoop(originTrials));
     }
     return originTrials;
 }
 
 OriginTrials::OriginTrials(ExecutionContext* host)
     : OriginTrialsBase(host) {}
 
+// static
+void OriginTrials::setTrialTokensFromHeader(ExecutionContext* executionContext, const String& headerValue)
+{
+    if (headerValue.isEmpty()) return;

[iclelland, 2016/04/05 17:01:30]

I don't know how much we care about formatting in generated code, but if I try
this in a blink cpp file, the presubmit hooks make me move the return to another
line.

[Marijn Kruisselbrink, 2016/04/05 23:57:00]

Yeah, was already fixed in the patch I uploaded yesterday (by no longer
modifying any of the generated code).

+    from(executionContext)->loadTokensFromHeader(headerValue);
+}
+
 {% for feature in features %}
 {% if feature.origin_trial_feature_name %}
 
 // static
 bool OriginTrials::{{feature.first_lowered_name}}Enabled(ExecutionContext* executionContext, String& errorMessage) {
     return OriginTrials::from(executionContext)->{{feature.first_lowered_name}}EnabledImpl(&errorMessage);
 }
 
 // static
 bool OriginTrials::{{feature.first_lowered_name}}Enabled(ExecutionContext* executionContext) {
@@ skipping 13 matching lines @@
 }
 {% endif %}
 {% endfor %}
 
 DEFINE_TRACE(OriginTrials)
 {
     OriginTrialsBase::trace(visitor);
 }
 
 } // namespace blink