Support loading trial tokens from HTTP headers.

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 1b4b6772a2957519e527e8b250413092b5d323fa..0aa0242d547d7d29462f11eaf337ef06430fd302 100644
--- a/third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h
+++ b/third_party/WebKit/Source/core/origin_trials/OriginTrialContext.h
@@ -39,6 +39,13 @@ public:
     static const char* supplementName();
     static OriginTrialContext* from(ExecutionContext*);
 
+    // Parses an Origin-Trial header as specified in
+    // https://jpchase.github.io/OriginTrials/#header into individual tokens.
+    // Returns null if the header value was malformed.
+    static PassOwnPtr<Vector<String>> parseHeaderValue(const String& headerValue);

[chasej, 2016/04/21 18:24:30]

Should this be using std::unique_ptr? The recent PSA said unique_ptr can be used
in Blink:
https://groups.google.com/a/chromium.org/forum/?pli=1#!searchin/blink-dev/uni...

[Marijn Kruisselbrink, 2016/04/21 20:27:09]

Good point, done.

+
+    static void addTokensFromHeader(ExecutionContext*, const String& headerValue);
+
     void addToken(const String& token);
 
     // Returns true if the feature should be considered enabled for the current