Make --force-fieldtrials not activate them in the browser process.

This is to make this testing flag more consistent with what happens
with a server-side field trial, so that the field trial doesn't
appear in about:version until client code explicitly queries its
state via a group() call.

Does not change the behaviour of the --force-fieldtrials flag
when passes to the renderer process, where it does need to
activate the trials so that they show up in crash reports, etc.

BUG=255142
TEST=Start a debug build of Chrome with the command line
flag --force-fieldtrials=Bat/Man/ and check that it doesn't
show up in chrome://version.

Review URL: https://chromiumcodereview.appspot.com/17945002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@209795 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 14 insertions, 12 deletions

diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index 99e40d4..8de46fd 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -610,11 +610,13 @@ void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
   // Ensure any field trials specified on the command line are initialized.
   // Also stop the metrics service so that we don't pollute UMA.
   if (command_line->HasSwitch(switches::kForceFieldTrials)) {
-    std::string persistent = command_line->GetSwitchValueASCII(
-        switches::kForceFieldTrials);
-    bool ret = base::FieldTrialList::CreateTrialsFromString(persistent);
-    CHECK(ret) << "Invalid --" << switches::kForceFieldTrials <<
-                  " list specified.";
+    // Create field trials without activating them, so that this behaves in a
+    // consistent manner with field trials created from the server.
+    bool result = base::FieldTrialList::CreateTrialsFromString(
+        command_line->GetSwitchValueASCII(switches::kForceFieldTrials),
+        base::FieldTrialList::DONT_ACTIVATE_TRIALS);
+    CHECK(result) << "Invalid --" << switches::kForceFieldTrials
+                  << " list specified.";
   }
 
   chrome_variations::VariationsService* variations_service =
diff --git a/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc b/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
index a4a36ca..1794fc2 100644
--- a/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
+++ b/chrome/browser/extensions/api/metrics_private/metrics_apitest.cc
@@ -127,7 +127,7 @@ void ValidateHistograms(const RecordedHistogram* recorded,
 IN_PROC_BROWSER_TEST_F(ExtensionApiTest, Metrics) {
   UserActionObserver observer;
 
-  base::FieldTrialList::CreateTrialsFromString("apitestfieldtrial2/group1/");
+  base::FieldTrialList::CreateFieldTrial("apitestfieldtrial2", "group1");
 
   ASSERT_TRUE(RunComponentExtensionTest("metrics")) << message_;
 
diff --git a/chrome/browser/search/search_unittest.cc b/chrome/browser/search/search_unittest.cc
index fb3acc0..91c6cfc 100644
--- a/chrome/browser/search/search_unittest.cc
+++ b/chrome/browser/search/search_unittest.cc
@@ -151,8 +151,8 @@ TEST_F(InstantExtendedAPIEnabledTest, EnabledViaCommandLineFlag) {
 }
 
 TEST_F(InstantExtendedAPIEnabledTest, EnabledViaFinchFlag) {
-  ASSERT_TRUE(base::FieldTrialList::CreateTrialsFromString(
-      "InstantExtended/Group1 espv:42/"));
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial("InstantExtended",
+                                                     "Group1 espv:42"));
   EXPECT_TRUE(IsInstantExtendedAPIEnabled());
   EXPECT_EQ(42ul, EmbeddedSearchPageVersion());
   ValidateMetrics(INSTANT_EXTENDED_NOT_SET);
@@ -160,8 +160,8 @@ TEST_F(InstantExtendedAPIEnabledTest, EnabledViaFinchFlag) {
 
 TEST_F(InstantExtendedAPIEnabledTest, DisabledViaCommandLineFlag) {
   GetCommandLine()->AppendSwitch(switches::kDisableInstantExtendedAPI);
-  ASSERT_TRUE(base::FieldTrialList::CreateTrialsFromString(
-      "InstantExtended/Group1 espv:2/"));
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial("InstantExtended",
+                                                     "Group1 espv:2"));
   EXPECT_FALSE(IsInstantExtendedAPIEnabled());
   EXPECT_EQ(0ul, EmbeddedSearchPageVersion());
   ValidateMetrics(INSTANT_EXTENDED_OPT_OUT);
@@ -451,8 +451,8 @@ TEST_F(SearchTest, IsInstantCheckboxEnabledExtendedEnabledWithInstant) {
   EnableInstantExtendedAPIForTesting();
 
   // Enable Instant.
-  ASSERT_TRUE(base::FieldTrialList::CreateTrialsFromString(
-      "InstantExtended/Group1 allow_instant:1/"));
+  ASSERT_TRUE(base::FieldTrialList::CreateFieldTrial("InstantExtended",
+                                                     "Group1 allow_instant:1"));
   ASSERT_TRUE(IsInstantCheckboxVisible());
 
   // Enable suggest.