Allow origin trials to be enabled by script

third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h

Index: third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h
diff --git a/third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h b/third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h
index cef1f0b3820ccc8cf036a089df88222034e40122..5c4ed4c6735a709a267d88f03d113d896d663b93 100644
--- a/third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h
+++ b/third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h
@@ -71,21 +71,25 @@ class CORE_EXPORT OriginTrialContext final
   // controls) should be considered enabled for the current execution context.
   bool isTrialEnabled(const String& trialName);
 
-  // Installs JavaScript bindings on the Window object for any features which
+  // Installs JavaScript bindings on the relevant objects for any features which
   // should be enabled by the current set of trial tokens. This method is called
-  // every time a token is added to the document, so that global interfaces will
-  // be properly visible, even if the V8 context is being reused (i.e., after
-  // navigation). If the V8 context is not initialized, this method will return
-  // without doing anything.
+  // every time a token is added to the document (including when tokens are
+  // added via script). JavaScript-exposed members will be properly visible,
+  // for existing objects in the V8 context, or even if the V8 context is being
+  // reused (i.e., after navigation). If the V8 context is not initialized, or
+  // there are no enabled trials, this method returns without doing anything.

[iclelland, 2017/01/26 20:14:12]

Can this method be called safely multiple times, if no new trials have been
enabled? We should call that out here, if so.

[chasej, 2017/01/27 17:22:36]

Done.

   void initializePendingFeatures();
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
-  void validateToken(const String& token);
+  // Validate the trial token, and return true if valid. If valid, the trial
+  // named in the token is also added to the list of enabled trials.
+  bool validateToken(const String& token);

[iclelland, 2017/01/26 20:14:12]

Maybe we should rename this to reflect its very relevant side effect --
something like "enableTrialFromToken", and document that it returns false if the
token was invalid?

[chasej, 2017/01/27 17:22:36]

Good idea! Done.

 
   Vector<String> m_tokens;
   HashSet<String> m_enabledTrials;
+  HashSet<String> m_installedTrials;
   WebTrialTokenValidator* m_trialTokenValidator;
 };