[omnibox] add a Finch flag to allow on device head suggest in incognito mode.

Bug: 925072
Change-Id: I8b9f355f33d95e7a35510eae8d5a671544f7fe6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1784354Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Ce Chen <cch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693927}

components/omnibox/browser/omnibox_field_trial.cc

@@ -680,6 +680,11 @@ bool OmniboxFieldTrial::IsOmniboxWrapPopupPositionEnabled() {
   return base::FeatureList::IsEnabled(omnibox::kOmniboxWrapPopupPosition);
 }
 
+bool OmniboxFieldTrial::IsOnDeviceHeadProviderEnabledForIncognito() {
+  return base::GetFieldTrialParamByFeatureAsBool(omnibox::kOnDeviceHeadProvider,
+                                                 "EnableForIncongnito", false);
+}
+
 const char OmniboxFieldTrial::kBundledExperimentFieldTrialName[] =
     "OmniboxBundledExperimentV1";
 const char OmniboxFieldTrial::kDisableProvidersRule[] = "DisableProviders";

components/omnibox/browser/omnibox_field_trial.h

@@ -421,6 +421,9 @@ bool IsMaxURLMatchesFeatureEnabled();
 // between top and bottom is enabled.
 bool IsOmniboxWrapPopupPositionEnabled();
 
+// Returns whether on device head provider is enabled for incognito mode.
+bool IsOnDeviceHeadProviderEnabledForIncognito();
+
 // ---------------------------------------------------------
 // Clipboard URL suggestions:
 

components/omnibox/browser/on_device_head_provider.cc

@@ -18,6 +18,7 @@
 #include "base/trace_event/trace_event.h"
 #include "components/omnibox/browser/autocomplete_provider_listener.h"
 #include "components/omnibox/browser/base_search_provider.h"
+#include "components/omnibox/browser/omnibox_field_trial.h"
 #include "components/omnibox/browser/on_device_head_provider.h"
 #include "components/omnibox/common/omnibox_features.h"
 #include "components/search_engines/search_terms_data.h"
@@ -103,8 +104,14 @@ bool OnDeviceHeadProvider::IsOnDeviceHeadProviderAllowed(
       input.type() == metrics::OmniboxInputType::EMPTY)
     return false;
 
-  // Make sure search suggest is enabled and user is not in incognito.
-  if (client()->IsOffTheRecord() || !client()->SearchSuggestEnabled())
+  // Check whether search suggest is enabled.
+  if (!client()->SearchSuggestEnabled())
+    return false;
+
+  // Make sure user is not in incognito, unless on device head provider is
+  // enabled for incognito.
+  if (client()->IsOffTheRecord() &&
+      !OmniboxFieldTrial::IsOnDeviceHeadProviderEnabledForIncognito())
     return false;
 
   // Reject on focus request.

components/omnibox/browser/on_device_head_provider_unittest.cc

@@ -107,6 +107,7 @@ TEST_F(OnDeviceHeadProviderTest, RejectIncognito) {
   input.set_want_asynchronous_matches(true);
 
   EXPECT_CALL(*client_.get(), IsOffTheRecord()).WillOnce(Return(true));
+  EXPECT_CALL(*client_.get(), SearchSuggestEnabled()).WillOnce(Return(true));
 
   provider_->Start(input, false);
   if (!provider_->done())