Adds a field trial flag to control whether to use an alternate Instant search...

Adds a field trial flag to control whether to use an alternate Instant search base page URL for prefetching search results.

BUG=382694
TEST=Run chrome with the following field trial flag and observe the Instant search base page url.
     --force-fieldtrials="EmbeddedSearch/Group1 use_alternate_instant_url:1 /"

Review URL: https://codereview.chromium.org/330653004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278824 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/search/search.cc

@@ -75,6 +75,12 @@ const char kPrerenderInstantUrlOnOmniboxFocus[] =
 // search query.
 const char kReuseInstantSearchBasePage[] = "reuse_instant_search_base_page";
 
+// Controls whether to use the alternate Instant search base URL. This allows
+// experimentation of Instant search.
+const char kUseAltInstantURL[] = "use_alternate_instant_url";
+const char kAltInstantURLPath[] = "search";
+const char kAltInstantURLQueryParams[] = "&qbp=1";
+
 const char kDisplaySearchButtonFlagName[] = "display_search_button";
 const char kOriginChipFlagName[] = "origin_chip";
 #if !defined(OS_IOS) && !defined(OS_ANDROID)
@@ -551,6 +557,15 @@ GURL GetInstantURL(Profile* profile, int start_margin,
   if (!IsURLAllowedForSupervisedUser(instant_url, profile))
     return GURL();
 
+  if (ShouldUseAltInstantURL()) {
+    GURL::Replacements replacements;
+    const std::string path(kAltInstantURLPath);
+    replacements.SetPathStr(path);
+    const std::string query(
+        instant_url.query() + std::string(kAltInstantURLQueryParams));
+    replacements.SetQueryStr(query);
+    instant_url = instant_url.ReplaceComponents(replacements);
+  }
   return instant_url;
 }
 
@@ -844,4 +859,10 @@ bool GetBoolValueForFlagWithDefault(const std::string& flag,
   return !!GetUInt64ValueForFlagWithDefault(flag, default_value ? 1 : 0, flags);
 }
 
+bool ShouldUseAltInstantURL() {
+  FieldTrialFlags flags;
+  return GetFieldTrialInfo(&flags) && GetBoolValueForFlagWithDefault(
+      kUseAltInstantURL, false, flags);
+}
+
 }  // namespace chrome

chrome/browser/search/search.h

@@ -289,6 +289,11 @@ bool GetBoolValueForFlagWithDefault(const std::string& flag,
 // Returns the Cacheable New Tab Page URL for the given |profile|.
 GURL GetNewTabPageURL(Profile* profile);
 
+// Returns true if 'use_alternate_instant_url' flag is set to true in field
+// trials to use an alternate Instant search base page URL for prefetching
+// search results. This allows experimentation of Instant search.
+bool ShouldUseAltInstantURL();
+
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SEARCH_SEARCH_H_

chrome/browser/search/search_unittest.cc

@@ -589,6 +589,13 @@ TEST_F(SearchTest, GetInstantURL) {
   // Disable suggest. No Instant URL.
   profile()->GetPrefs()->SetBoolean(prefs::kSearchSuggestEnabled, false);
   EXPECT_EQ(GURL(), GetInstantURL(profile(), kDisableStartMargin, false));
+
+  // Use alternate Instant search base URL.
+  profile()->GetPrefs()->SetBoolean(prefs::kSearchSuggestEnabled, true);
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
+      "EmbeddedSearch", "Group1 espv:8 use_alternate_instant_url:1"));
+  EXPECT_EQ(GURL("https://foo.com/search?foo=foo&qbp=1#foo=foo&strk"),
+            GetInstantURL(profile(), kDisableStartMargin, false));
 }
 
 TEST_F(SearchTest, StartMarginCGI) {
@@ -724,6 +731,18 @@ TEST_F(SearchTest, ShouldAllowPrefetchNonDefaultMatch_EnabledViaFieldTrial) {
   EXPECT_EQ(80ul, EmbeddedSearchPageVersion());
 }
 
+TEST_F(SearchTest, ShouldUseAltInstantURL_DisabledViaFieldTrial) {
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
+      "EmbeddedSearch", "Group1 espv:8 use_alternate_instant_url:0"));
+  EXPECT_FALSE(ShouldUseAltInstantURL());
+}
+
+TEST_F(SearchTest, ShouldUseAltInstantURL_EnabledViaFieldTrial) {
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(
+      "EmbeddedSearch", "Group1 espv:8 use_alternate_instant_url:1"));
+  EXPECT_TRUE(ShouldUseAltInstantURL());
+}
+
 TEST_F(SearchTest,
        ShouldPrerenderInstantUrlOnOmniboxFocus_PrefetchResultsFlagDisabled) {
   ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial(