Introduce dynamic ablation of AutocompleteProviders using AC dynamic trials.

chrome/browser/autocomplete/autocomplete_field_trial_unittest.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/autocomplete/autocomplete_field_trial.h"
+
+#include "base/basictypes.h"
+#include "base/metrics/field_trial.h"
+#include "base/string16.h"
+#include "chrome/common/metrics/entropy_provider.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+class AutocompleteFieldTrialTest : public testing::Test {
+ public:
+  AutocompleteFieldTrialTest() {}
+
+  static void SetUpTestCase() {
+    field_trial_list_ = new base::FieldTrialList(
+        new metrics::SHA1EntropyProvider("foo"));
+    AutocompleteFieldTrial::ActivateDynamicTrials();
+  }
+
+  static void TearDownTestCase() {
+    delete field_trial_list_;
+  }
+
+  // Creates and activates a field trial.
+  static base::FieldTrial* CreateTestTrial(const std::string& name,
+                                           const std::string& group_name) {
+    base::FieldTrial* trial = base::FieldTrialList::CreateFieldTrial(
+        name, group_name);
+    trial->group();
+    return trial;
+  }
+
+ private:
+  // Needed for Activate{Static/Dynamic}Trials().
+  static base::FieldTrialList* field_trial_list_;

[Mark P, 2013/02/11 22:39:46]

Consider making this a non-pointer, non-static member as in
https://code.google.com/codesearch#OAMlx_jo-ck/src/chrome/common/metrics/vari...

[Bart N., 2013/02/12 01:18:19]

As discussed offline, I wanted to avoid initialization in each test method. I
know we currently have only 1, but if we add more coverage, we would have to do
it each time. 

+
+  DISALLOW_COPY_AND_ASSIGN(AutocompleteFieldTrialTest);
+};
+
+// static
+base::FieldTrialList* AutocompleteFieldTrialTest::field_trial_list_ = NULL;
+
+// Test if GetDisabledProviderTypes() properly parses various field trial
+// group names.
+// Note: Unfortunately, it's not possible to disable an already reported
+// field trial group, so the following test gradually adds more field trials
+// as it goes.

[Mark P, 2013/02/11 22:39:46]

If you want to disable already reported groups, you can use a strategy like
this:
https://code.google.com/codesearch#OAMlx_jo-ck/src/chrome/browser/chrome_brow...

[Bart N., 2013/02/12 01:18:19]

I actually found a better way. I've added ResetFieldTrialList method, so I can
clean the state between various checks.

[Mark P, 2013/02/12 17:53:31]

Nice.

+TEST_F(AutocompleteFieldTrialTest, GetDisabledProviderTypes) {
+  EXPECT_EQ(0, AutocompleteFieldTrial::GetDisabledProviderTypes());
+
+  // Invalid groups.
+  base::FieldTrial* trial = CreateTestTrial("AutocompleteDynamicTrial_0",
+                                            "Group1 DisabledProviders_");
+  EXPECT_EQ(0, AutocompleteFieldTrial::GetDisabledProviderTypes());
+  trial = CreateTestTrial("AutocompleteDynamicTrial_1",
+                          "Group1 DisabledProviders_XXX");
+  EXPECT_EQ(0, AutocompleteFieldTrial::GetDisabledProviderTypes());
+
+  // Valid group name, unsupported trial name.
+  trial = CreateTestTrial("UnsupportedTrialName",
+                          "Group1 DisabledProviders_20");
+  EXPECT_EQ(0, AutocompleteFieldTrial::GetDisabledProviderTypes());
+
+  // Valid field and group name.
+  trial = CreateTestTrial("AutocompleteDynamicTrial_2",
+                          "Group1 DisabledProviders_3");
+  EXPECT_EQ(3, AutocompleteFieldTrial::GetDisabledProviderTypes());
+  // Two groups should be OR-ed together.
+  trial = CreateTestTrial("AutocompleteDynamicTrial_3",
+                          "Group1 DisabledProviders_6");
+  EXPECT_EQ(7, AutocompleteFieldTrial::GetDisabledProviderTypes());
+}