Adding a local predictor field trial, and a facility

to report local predictor stats based on a whitelist of
URL hashes (only placeholder dummy file for now).
R=shishir@chromium.org
Review URL: https://codereview.chromium.org/11364034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@165696 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 98 insertions, 0 deletions

diff --git a/chrome/browser/browser_resources.grd b/chrome/browser/browser_resources.grd
index bffa941..6b46316 100644
--- a/chrome/browser/browser_resources.grd
+++ b/chrome/browser/browser_resources.grd
@@ -157,6 +157,8 @@
       <include name="IDR_POLICY_CSS" file="resources\policy.css" type="BINDATA"/>
       <include name="IDR_POLICY_HTML" file="resources\policy.html" flattenhtml="true" allowexternalscript="true" type="BINDATA"/>
       <include name="IDR_POLICY_JS" file="resources\policy.js" type="BINDATA"/>
+      <include name="IDR_PRERENDER_URL_WHITELIST"
+	       file="resources\prerender_url_whitelist.dat" type="BINDATA"/>
       <if expr="pp_ifdef('enable_printing')">
         <include name="IDR_PRINT_PREVIEW_HTML" file="resources\print_preview\print_preview.html" flattenhtml="true" allowexternalscript="true" type="BINDATA" />
         <include name="IDR_PRINT_PREVIEW_JS" file="resources\print_preview\print_preview.js" flattenhtml="true" type="BINDATA" />
diff --git a/chrome/browser/prerender/prerender_field_trial.cc b/chrome/browser/prerender/prerender_field_trial.cc
index 7938dca..15bd501 100644
--- a/chrome/browser/prerender/prerender_field_trial.cc
+++ b/chrome/browser/prerender/prerender_field_trial.cc
@@ -30,6 +30,9 @@ const char kSpeculativePrefetchingTrialName[] = "SpeculativePrefetching";
 int g_speculative_prefetching_learning_group = kint32min;
 int g_speculative_prefetching_prefetching_group = kint32min;
 
+const char kLocalPredictorTrialName[] = "PrerenderLocalPredictor";
+int g_local_predictor_default_group_number = kint32min;
+
 void SetupPrefetchFieldTrial() {
   chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
   if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
@@ -143,6 +146,7 @@ void SetupPrerenderFieldTrial() {
 
 void ConfigureOmniboxPrerender();
 void ConfigureSpeculativePrefetching();
+void ConfigureLocalPredictor();
 
 void ConfigurePrefetchAndPrerender(const CommandLine& command_line) {
   enum PrerenderOption {
@@ -204,6 +208,7 @@ void ConfigurePrefetchAndPrerender(const CommandLine& command_line) {
 
   ConfigureOmniboxPrerender();
   ConfigureSpeculativePrefetching();
+  ConfigureLocalPredictor();
 }
 
 void ConfigureOmniboxPrerender() {
@@ -333,4 +338,26 @@ bool IsSpeculativeResourcePrefetchingEnabled(Profile* profile) {
   return group == g_speculative_prefetching_prefetching_group;
 }
 
+void ConfigureLocalPredictor() {
+  const FieldTrial::Probability kDivisor = 100;
+
+  FieldTrial::Probability kEnableProbability = 90;
+  chrome::VersionInfo::Channel channel = chrome::VersionInfo::GetChannel();
+  if (channel == chrome::VersionInfo::CHANNEL_STABLE ||
+      channel == chrome::VersionInfo::CHANNEL_BETA) {
+    kEnableProbability = 1;
+  }
+  scoped_refptr<FieldTrial> local_predictor_trial(
+      FieldTrialList::FactoryGetFieldTrial(
+          kLocalPredictorTrialName, kDivisor, "Disabled",
+          2013, 12, 31, &g_local_predictor_default_group_number));
+  local_predictor_trial->AppendGroup("Enabled", kEnableProbability);
+}
+
+bool IsLocalPredictorEnabled() {
+  const int group = FieldTrialList::FindValue(kLocalPredictorTrialName);
+  return (group != FieldTrial::kNotFinalized &&
+          group != g_omnibox_trial_default_group_number);
+}
+
 }  // namespace prerender
diff --git a/chrome/browser/prerender/prerender_field_trial.h b/chrome/browser/prerender/prerender_field_trial.h
index 3cd4fc3..3efcbad 100644
--- a/chrome/browser/prerender/prerender_field_trial.h
+++ b/chrome/browser/prerender/prerender_field_trial.h
@@ -29,6 +29,9 @@ bool IsSpeculativeResourcePrefetchingLearningEnabled(Profile* profile);
 // resource prefetching experiment.
 bool IsSpeculativeResourcePrefetchingEnabled(Profile* profile);
 
+// Returns true iff the Prerender Local Predictor is enabled.
+bool IsLocalPredictorEnabled();
+
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_FIELD_TRIAL_H_
diff --git a/chrome/browser/prerender/prerender_local_predictor.cc b/chrome/browser/prerender/prerender_local_predictor.cc
index d7fdfc9..cf371ee 100644
--- a/chrome/browser/prerender/prerender_local_predictor.cc
+++ b/chrome/browser/prerender/prerender_local_predictor.cc
@@ -23,6 +23,9 @@
 #include "chrome/browser/history/history_service_factory.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/common/page_transition_types.h"
+#include "crypto/secure_hash.h"
+#include "grit/browser_resources.h"
+#include "ui/base/resource/resource_bundle.h"
 
 using content::BrowserThread;
 using content::PageTransition;
@@ -32,6 +35,8 @@ namespace prerender {
 
 namespace {
 
+static const size_t kURLHashSize = 5;
+
 // Task to lookup the URL for a given URLID.
 class GetURLForURLIDTask : public HistoryDBTask {
  public:
@@ -144,6 +149,24 @@ bool IsRootPageURL(const GURL& url) {
     (!url.has_ref());
 }
 
+int64 URLHashToInt64(const unsigned char* data) {
+  COMPILE_ASSERT(kURLHashSize < sizeof(int64), url_hash_must_fit_in_int64);
+  int64 value = 0;
+  memcpy(&value, data, kURLHashSize);
+  return value;
+}
+
+int64 GetInt64URLHashForURL(const GURL& url) {
+  COMPILE_ASSERT(kURLHashSize < sizeof(int64), url_hash_must_fit_in_int64);
+  scoped_ptr<crypto::SecureHash> hash(
+      crypto::SecureHash::Create(crypto::SecureHash::SHA256));
+  int64 hash_value = 0;
+  const char* url_string = url.spec().c_str();
+  hash->Update(url_string, strlen(url_string));
+  hash->Finish(&hash_value, kURLHashSize);
+  return hash_value;
+}
+
 }  // namespace
 
 struct PrerenderLocalPredictor::PrerenderData {
@@ -183,6 +206,33 @@ PrerenderLocalPredictor::PrerenderLocalPredictor(
                  &PrerenderLocalPredictor::Init);
     RecordEvent(EVENT_INIT_SCHEDULED);
   }
+
+  static const size_t kChecksumHashSize = 32;
+  base::RefCountedStaticMemory* url_whitelist_data =
+      ResourceBundle::GetSharedInstance().LoadDataResourceBytes(
+          IDR_PRERENDER_URL_WHITELIST, ui::SCALE_FACTOR_NONE);
+  size_t size = url_whitelist_data->size();
+  const unsigned char* front = url_whitelist_data->front();
+  if (size < kChecksumHashSize ||
+      (size - kChecksumHashSize) % kURLHashSize != 0) {
+    RecordEvent(EVENT_URL_WHITELIST_ERROR);
+    return;
+  }
+  scoped_ptr<crypto::SecureHash> hash(
+      crypto::SecureHash::Create(crypto::SecureHash::SHA256));
+  hash->Update(front + kChecksumHashSize, size - kChecksumHashSize);
+  char hash_value[kChecksumHashSize];
+  hash->Finish(hash_value, kChecksumHashSize);
+  if (memcmp(hash_value, front, kChecksumHashSize)) {
+    RecordEvent(EVENT_URL_WHITELIST_ERROR);
+    return;
+  }
+  for (const unsigned char* p = front + kChecksumHashSize;
+       p < front + size;
+       p += kURLHashSize) {
+    url_whitelist_.insert(URLHashToInt64(p));
+  }
+  RecordEvent(EVENT_URL_WHITELIST_OK);
 }
 
 PrerenderLocalPredictor::~PrerenderLocalPredictor() {
@@ -318,6 +368,11 @@ void PrerenderLocalPredictor::OnLookupURL(history::URLID url_id,
     }
   }
 
+  if (url_whitelist_.count(GetInt64URLHashForURL(url)) > 0) {
+    RecordEvent(EVENT_PRERENDER_URL_LOOKUP_RESULT_ON_WHITELIST);
+    if (IsRootPageURL(url))
+      RecordEvent(EVENT_PRERENDER_URL_LOOKUP_RESULT_ON_WHITELIST_ROOT_PAGE);
+  }
   if (IsRootPageURL(url))
     RecordEvent(EVENT_PRERENDER_URL_LOOKUP_RESULT_ROOT_PAGE);
   if (url.SchemeIs("http"))
diff --git a/chrome/browser/prerender/prerender_local_predictor.h b/chrome/browser/prerender/prerender_local_predictor.h
index 4543aed..375fdf6 100644
--- a/chrome/browser/prerender/prerender_local_predictor.h
+++ b/chrome/browser/prerender/prerender_local_predictor.h
@@ -7,6 +7,7 @@
 
 #include <vector>
 
+#include "base/hash_tables.h"
 #include "base/timer.h"
 #include "chrome/browser/common/cancelable_request.h"
 #include "chrome/browser/history/visit_database.h"
@@ -47,6 +48,10 @@ class PrerenderLocalPredictor : public history::VisitDatabaseObserver {
     EVENT_PRERENDER_URL_LOOKUP_RESULT_CONTAINS_LOGIN = 19,
     EVENT_START_URL_LOOKUP = 20,
     EVENT_ADD_VISIT_NOT_ROOTPAGE = 21,
+    EVENT_URL_WHITELIST_ERROR = 22,
+    EVENT_URL_WHITELIST_OK = 23,
+    EVENT_PRERENDER_URL_LOOKUP_RESULT_ON_WHITELIST = 24,
+    EVENT_PRERENDER_URL_LOOKUP_RESULT_ON_WHITELIST_ROOT_PAGE = 25,
     EVENT_MAX_VALUE
   };
 
@@ -95,6 +100,8 @@ class PrerenderLocalPredictor : public history::VisitDatabaseObserver {
   scoped_ptr<PrerenderData> current_prerender_;
   scoped_ptr<PrerenderData> last_swapped_in_prerender_;
 
+  base::hash_set<int64> url_whitelist_;
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderLocalPredictor);
 };
 
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index 4c25663..342bf34 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -200,6 +200,9 @@ PrerenderManager::PrerenderManager(Profile* profile,
   // the same thread that it was created on.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
+  if (IsLocalPredictorEnabled())
+    local_predictor_.reset(new PrerenderLocalPredictor(this));
+
   // Certain experiments override our default config_ values.
   switch (PrerenderManager::GetMode()) {
     case PrerenderManager::PRERENDER_MODE_EXPERIMENT_MULTI_PRERENDER_GROUP:
diff --git a/chrome/browser/resources/prerender_url_whitelist.dat b/chrome/browser/resources/prerender_url_whitelist.dat
new file mode 100644
index 0000000..573541a
--- /dev/null
+++ b/chrome/browser/resources/prerender_url_whitelist.dat
@@ -0,0 +1 @@
+0