Add ExternalPrerenderRequestHandler and related API

chrome/browser/prerender/prerender_histograms.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/prerender/prerender_histograms.h"
 
 #include <string>
 
 #include "base/format_macros.h"
 #include "base/metrics/histogram.h"
@@ skipping 40 matching lines @@
     case ORIGIN_OMNIBOX:
       return ComposeHistogramName("omnibox", name);
     case ORIGIN_NONE:
       return ComposeHistogramName("none", name);
     case ORIGIN_LINK_REL_PRERENDER_SAMEDOMAIN:
       return ComposeHistogramName("websame", name);
     case ORIGIN_LINK_REL_PRERENDER_CROSSDOMAIN:
       return ComposeHistogramName("webcross", name);
     case ORIGIN_LOCAL_PREDICTOR:
       return ComposeHistogramName("localpredictor", name);
+    case ORIGIN_EXTERNAL_REQUEST:
+        return ComposeHistogramName("externalrequest", name);
     case ORIGIN_GWS_PRERENDER:  // Handled above.
     default:
       NOTREACHED();
       break;
   };
 
   // Dummy return value to make the compiler happy.
   NOTREACHED();
   return ComposeHistogramName("wash", name);
 }
@@ skipping 39 matching lines @@
   } else if (origin == ORIGIN_OMNIBOX) { \
     HISTOGRAM; \
   } else if (origin == ORIGIN_NONE) { \
     HISTOGRAM; \
   } else if (origin == ORIGIN_LINK_REL_PRERENDER_SAMEDOMAIN) { \
     HISTOGRAM; \
   } else if (origin == ORIGIN_LINK_REL_PRERENDER_CROSSDOMAIN) { \
     HISTOGRAM; \
   } else if (origin == ORIGIN_LOCAL_PREDICTOR) { \
     HISTOGRAM; \
+  } else if (origin == ORIGIN_EXTERNAL_REQUEST) { \
+    HISTOGRAM; \
   } else if (experiment != kNoExperiment) { \
     HISTOGRAM; \
   } else { \
     HISTOGRAM; \
   } \
 }
 
 PrerenderHistograms::PrerenderHistograms()
     : last_experiment_id_(kNoExperiment),
       last_origin_(ORIGIN_MAX),
@@ skipping 255 matching lines @@
   return last_experiment_id_;
 }
 
 bool PrerenderHistograms::IsOriginExperimentWash() const {
   if (!WithinWindow())
     return false;
   return origin_experiment_wash_;
 }
 
 }  // namespace prerender