Enable QUIC for proxies based on Finch config and command line switch.

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index 1f969ec4a63fce5acf8c46d0cb821f4e939e9454..4dc090da2394b6353d15d99b01b4679e3fc239df 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -182,6 +182,7 @@ class IOThread : public content::BrowserThreadDelegate {
     Optional<double> alternate_protocol_probability_threshold;
 
     Optional<bool> enable_quic;
+    Optional<bool> enable_quic_for_proxies;
     Optional<bool> enable_quic_port_selection;
     Optional<bool> quic_always_require_handshake_confirmation;
     Optional<bool> quic_disable_connection_pooling;
@@ -235,6 +236,14 @@ class IOThread : public content::BrowserThreadDelegate {
 
   base::TimeTicks creation_time() const;
 
+  // Returns the name of QUIC trial group.
+  static std::string QuicTrialGroup();
+
+  // Returns true if QUIC should be enabled for proxies, either as a result
+  // of a field trial or a command line flag.
+  static bool ShouldEnableQuicForProxies(const base::CommandLine& command_line,
+                                         base::StringPiece quic_trial_group);
+
  private:
   // Map from name to value for all parameters associate with a field trial.
   typedef std::map<std::string, std::string> VariationParameters;