Remove Finch config control for contextual search.

BUG=679349

Review-Url: https://codereview.chromium.org/2627663002
Cr-Commit-Position: refs/heads/master@{#442847}

ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator.h

@@ -42,9 +42,8 @@ typedef NS_ENUM(NSInteger, TouchToSearchPreferenceState) {
 // Touch-to-Search feature.
 @interface TouchToSearchPermissionsMediator : NSObject
 
-// YES if the device supports Touch-to-Search (based on command line flags and
-// Finch experiments). The return value will be the same over the lifetime of
-// a Chrome process.
+// YES if the device supports Touch-to-Search (based on command line flags). The
+// return value will be the same over the lifetime of a Chrome process.
 + (BOOL)isTouchToSearchAvailableOnDevice;
 
 // Designated initializer.

ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator.mm

@@ -9,7 +9,6 @@
 #include "base/command_line.h"
 #import "base/ios/weak_nsobject.h"
 #include "base/logging.h"
-#include "base/metrics/field_trial.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "components/prefs/pref_service.h"
 #include "components/search_engines/template_url_service.h"
@@ -24,9 +23,6 @@
 #include "net/base/network_change_notifier.h"
 
 namespace {
-// Field trial constants.
-const char kContextualSearchFieldTrialName[] = "ContextualSearchIOS";
-const char kContextualSearchFieldTrialEnabled[] = "Enabled";
 // Maps pref string values to state enum.
 const struct {
   const char* value;
@@ -68,22 +64,25 @@ const struct {
 @synthesize observing = _observing;
 
 + (BOOL)isTouchToSearchAvailableOnDevice {
-  // If the disable flag is flipped, the feature isn't available.
-  // If the enable flag is flipped, it's available.
-  // If the browser is in the field trial, it's available.
-  BOOL available = NO;
+  // By default the feature is not available. If the enable flag
+  // (switches::kEnableContextualSearch) is flipped, then it is available.
+  // The disable switch (switches::kDisableContextualSearch) is also supported,
+  // although it is only useful when Finch experiments are also supported.
+
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableContextualSearch)) {
+    // If both enable and disable flags are present, disable wins.
     return NO;
-  } else if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+  }
+
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableContextualSearch)) {
-    available = YES;
-  } else {
-    available =
-        base::FieldTrialList::FindFullName(kContextualSearchFieldTrialName) ==
-        kContextualSearchFieldTrialEnabled;
+    // Even if the command line flag is flipped, don't enable the feature if
+    // test hooks disable it.
+    return !tests_hook::DisableContextualSearch();
   }
-  return available && !tests_hook::DisableContextualSearch();
+
+  return NO;
 }
 
 - (instancetype)initWithBrowserState:(ios::ChromeBrowserState*)browserState {

ios/chrome/browser/ui/contextual_search/touch_to_search_permissions_mediator_unittest.mm

@@ -555,11 +555,14 @@ TEST(TouchToSearchPermissionsAvailabilityTest, CommandLinePermissions) {
 }
 
 TEST(TouchToSearchPermissionsAvailabilityTest, FieldTrial) {
+  // Field trial support is not currently supported, so it is expected
+  // that under all field trial configs, the feature will remain disabled.
+  // If field trial support is added back in, this test should be updated.
   const struct {
     const std::string trial_group_name;
     bool expect_available;
   } tests[] = {
-      {"Enabled", true},
+      {"Enabled", false},
       {"Disabled", false},
       {"Control", false},
       {"Spadoinkle", false},