Prerender: exclude AGSA from the PrerenderSilence experiment

Currently AGSA only uses ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR. The experiment
will not take effect on these origins. Other 1st party apps are not using this
prerender::Origin, as far as we know, and the use of it is restricted to 1st
party, hence this change should not affect the experiment for other Android
apps.

BUG=640592

Review-Url: https://codereview.chromium.org/2600893002
Cr-Commit-Position: refs/heads/master@{#440750}

chrome/browser/prerender/prerender_manager.cc

@@ -1262,8 +1262,10 @@ void PrerenderManager::RecordNetworkBytes(Origin origin,
 }
 
 bool PrerenderManager::IsPrerenderSilenceExperiment(Origin origin) const {
-  if (origin == ORIGIN_OFFLINE)
+  if (origin == ORIGIN_OFFLINE ||
+      origin == ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR) {
     return false;
+  }
 
   // The group name should contain expiration time formatted as:
   //   "ExperimentYes_expires_YYYY-MM-DDTHH:MM:SSZ".

chrome/browser/prerender/prerender_unittest.cc

@@ -1231,7 +1231,7 @@ TEST_F(PrerenderTest, PrerenderNotAllowedOnCellularWithExternalOrigin) {
   EXPECT_FALSE(prerender_contents->prerendering_has_started());
 }
 
-// Checks that the "PrerenderSilence experiment does not disable offline
+// Checks that the "PrerenderSilence" experiment does not disable offline
 // prerendering.
 TEST_F(PrerenderTest, PrerenderSilenceAllowsOffline) {
   // Set the time to 30 seconds before the experiment expires.
@@ -1252,13 +1252,36 @@ TEST_F(PrerenderTest, PrerenderSilenceAllowsOffline) {
   EXPECT_EQ(ORIGIN_OFFLINE, prerender_handle->contents()->origin());
 }
 
-// Checks that the "PrerenderSilence" experiment disables prerendering.
+// Checks that the "PrerenderSilence" experiment does not disable
+// forced-cellular prerendering.
+TEST_F(PrerenderTest, PrerenderSilenceAllowsForcedCellular) {
+  // Set the time to 30 seconds before the experiment expires.
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
+      "PrerenderSilence", "ExperimentYes_expires_2016-12-20T00:01:00Z"));
+  ASSERT_TRUE(OverridePrerenderManagerTime("2016-12-20T00:00:30Z",
+                                           prerender_manager()));
+  GURL url("http://www.google.com/");
+  DummyPrerenderContents* prerender_contents =
+      prerender_manager()->CreateNextPrerenderContents(
+          url, ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR,
+          FINAL_STATUS_MANAGER_SHUTDOWN);
+  std::unique_ptr<PrerenderHandle> prerender_handle =
+      prerender_manager()->AddPrerenderOnCellularFromExternalRequest(
+          url, content::Referrer(), nullptr, gfx::Rect(kSize));
+  EXPECT_TRUE(prerender_handle);
+  EXPECT_TRUE(prerender_handle->IsPrerendering());
+  EXPECT_TRUE(prerender_contents->prerendering_has_started());
+  EXPECT_EQ(prerender_contents, prerender_handle->contents());
+  EXPECT_EQ(ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR,
+            prerender_handle->contents()->origin());
+}
+
+// Checks that the "PrerenderSilence" experiment disables prerendering and
+// re-enables it after expiration.
 TEST_F(PrerenderTest, PrerenderSilenceDisallowsNonOffline) {
   ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
       "PrerenderSilence", "ExperimentYes_expires_2016-12-20T00:02:00Z"));
-  ASSERT_TRUE(OverridePrerenderManagerTime("2016-12-20T00:01:00Z",
-                                           prerender_manager()));
-  const Origin origins[] = {
+  Origin prerender_silence_origins[] = {
       ORIGIN_GWS_PRERENDER,
       ORIGIN_OMNIBOX,
       ORIGIN_NONE,
@@ -1267,12 +1290,23 @@ TEST_F(PrerenderTest, PrerenderSilenceDisallowsNonOffline) {
       ORIGIN_EXTERNAL_REQUEST,
       ORIGIN_INSTANT,
       ORIGIN_LINK_REL_NEXT,
-      ORIGIN_EXTERNAL_REQUEST_FORCED_CELLULAR,
   };
-  for (const Origin& origin : origins) {
+
+  // Prerender before expiration of the experiment.
+  ASSERT_TRUE(OverridePrerenderManagerTime("2016-12-20T00:01:00Z",
+                                           prerender_manager()));
+  for (const Origin& origin : prerender_silence_origins) {
     EXPECT_TRUE(
         prerender_manager()->IsPrerenderSilenceExperimentForTesting(origin));
   }
+
+  // Prerender after expiration of the experiment.
+  ASSERT_TRUE(OverridePrerenderManagerTime("2016-12-20T00:03:00Z",
+                                           prerender_manager()));
+  for (const Origin& origin : prerender_silence_origins) {
+    EXPECT_FALSE(
+        prerender_manager()->IsPrerenderSilenceExperimentForTesting(origin));
+  }
 }
 
 // Checks that prerendering is enabled after expiration of the