tools: Local tests for the speculative prefetch predictor.

chrome/browser/predictors/resource_prefetch_common.cc

Index: chrome/browser/predictors/resource_prefetch_common.cc
diff --git a/chrome/browser/predictors/resource_prefetch_common.cc b/chrome/browser/predictors/resource_prefetch_common.cc
index 2b97faf37164dbda4be152bfa7ef840985061557..d68ecd959bc3609f6e09847f600e99d42fda1ffa 100644
--- a/chrome/browser/predictors/resource_prefetch_common.cc
+++ b/chrome/browser/predictors/resource_prefetch_common.cc
@@ -25,8 +25,17 @@ using std::vector;
 
 namespace predictors {
 
-const char kSpeculativePrefetchingTrialName[] =
+namespace {
+constexpr int kUrlHostLearningMode =
+    ResourcePrefetchPredictorConfig::URL_LEARNING |
+    ResourcePrefetchPredictorConfig::HOST_LEARNING;
+constexpr int kUrlHostPrefetchingMode =
+    ResourcePrefetchPredictorConfig::URL_PREFETCHING |
+    ResourcePrefetchPredictorConfig::HOST_PREFETCHING;
+
+constexpr char kSpeculativePrefetchingTrialName[] =
     "SpeculativeResourcePrefetching";
+}  // namespace
 
 /*
  * SpeculativeResourcePrefetching is a field trial, and its value must have the
@@ -68,14 +77,15 @@ bool IsSpeculativeResourcePrefetchingEnabled(
     if (value == switches::kSpeculativeResourcePrefetchingDisabled) {
       return false;
     } else if (value == switches::kSpeculativeResourcePrefetchingLearning) {
-      config->mode |= ResourcePrefetchPredictorConfig::URL_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
+      config->mode |= kUrlHostLearningMode;
+      return true;
+    } else if (value ==
+               switches::kSpeculativeResourceExternalPrefetchingEnabled) {
+      config->mode |= kUrlHostLearningMode | kUrlHostPrefetchingMode;

[pasko, 2016/11/24 19:31:16]

why setting kUrlHostPrefetchingMode bit here? I thought it would be ignored via
EXTERNAL_ONLY. Is it going to be ignored only sometimes?

+      config->mode |= ResourcePrefetchPredictorConfig::EXTERNAL_ONLY;
       return true;
     } else if (value == switches::kSpeculativeResourcePrefetchingEnabled) {
-      config->mode |= ResourcePrefetchPredictorConfig::URL_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::URL_PREFETCHING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_PRFETCHING;
+      config->mode |= kUrlHostLearningMode;

[pasko, 2016/11/24 19:31:16]

why only learning is enabled here?

[Benoit L, 2016/11/30 12:08:27]

Done.

       return true;
     }
   }
@@ -100,8 +110,7 @@ bool IsSpeculativeResourcePrefetchingEnabled(
       config->mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
     } else {
       // Default: both Url and Host
-      config->mode |= ResourcePrefetchPredictorConfig::URL_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
+      config->mode |= kUrlHostLearningMode;
     }
   } else if (spec_prefetching == "Enabled") {
     if (spec_predictor == "Url") {
@@ -109,13 +118,10 @@ bool IsSpeculativeResourcePrefetchingEnabled(
       config->mode |= ResourcePrefetchPredictorConfig::URL_PREFETCHING;
     } else if (spec_predictor == "Host") {
       config->mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_PRFETCHING;
+      config->mode |= ResourcePrefetchPredictorConfig::HOST_PREFETCHING;
     } else {
       // Default: both Url and Host
-      config->mode |= ResourcePrefetchPredictorConfig::URL_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_LEARNING;
-      config->mode |= ResourcePrefetchPredictorConfig::URL_PREFETCHING;
-      config->mode |= ResourcePrefetchPredictorConfig::HOST_PRFETCHING;
+      config->mode |= kUrlHostLearningMode | kUrlHostPrefetchingMode;
     }
   } else {
     // Default: spec_prefetching == "Disabled"
@@ -220,6 +226,10 @@ bool ResourcePrefetchPredictorConfig::IsLearningEnabled() const {
   return IsURLLearningEnabled() || IsHostLearningEnabled();
 }
 
+bool ResourcePrefetchPredictorConfig::ExternalPrefetchingOnly() const {

[pasko, 2016/11/24 19:31:16]

I am confused by this name

"ExternalPrefetchingOnly" suggests to me that only external prefetching is
enabled by this config. At the same time the code asserts that learning is
allowed as well.

+  return (mode & EXTERNAL_ONLY) > 0;
+}
+
 bool ResourcePrefetchPredictorConfig::IsPrefetchingEnabled(
     Profile* profile) const {
   return IsURLPrefetchingEnabled(profile) || IsHostPrefetchingEnabled(profile);
@@ -252,7 +262,7 @@ bool ResourcePrefetchPredictorConfig::IsHostPrefetchingEnabled(
       chrome_browser_net::NetworkPredictionStatus::ENABLED) {
     return false;
   }
-  return (mode & HOST_PRFETCHING) > 0;
+  return (mode & HOST_PREFETCHING) > 0;
 }
 
 bool ResourcePrefetchPredictorConfig::IsLowConfidenceForTest() const {