Revert "assistant: Remove IsScreenContextQueryEnabled"

This reverts commit de6ebaa2.

Reason for revert: causes compile failure on linux-chromeos-chrome

Sample build: https://ci.chromium.org/p/chrome/builders/ci/linux-chromeos-chrome/3372

Sample log: https://logs.chromium.org/logs/chrome/buildbucket/cr-buildbucket.appspot.com/8887878986181186864/+/steps/compile/0/stdout?format=raw
---
[34344/60074] CXX obj/chromeos/services/assistant/lib/assistant_manager_service_impl.o
FAILED: obj/chromeos/services/assistant/lib/assistant_manager_service_impl.o
/b/s/w/ir/cache/goma/client/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF...(too long)
../../chromeos/services/assistant/assistant_manager_service_impl.cc:101:16: error: unused variable 'kScreenContextQuery' [-Werror,-Wunused-const-variable]
constexpr char kScreenContextQuery[] = "screen context";
^
1 error generated.
---

Original change's description:
> assistant: Remove IsScreenContextQueryEnabled
> 
> Remove unused code.
> 
> Bug: b/145218971
> Test: manual
> Change-Id: I54e08fc38e967517212b2f41fabe6bb872d17cf3
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067938
> Commit-Queue: Tao Wu <wutao@chromium.org>
> Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#743408}

TBR=xiaohuic@chromium.org,wutao@chromium.org

Change-Id: I565b31eb10ecaf53d9adae452320de420b7f00db
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: b/145218971
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2067761Reviewed-by: Takashi Sakamoto <tasak@google.com>
Commit-Queue: Takashi Sakamoto <tasak@google.com>
Cr-Commit-Position: refs/heads/master@{#743425}

chromeos/services/assistant/assistant_manager_service_impl.cc

@@ -1543,6 +1543,19 @@ void AssistantManagerServiceImpl::SendScreenContextRequest(
     ax::mojom::AssistantExtra* assistant_extra,
     ui::AssistantTree* assistant_tree,
     const std::vector<uint8_t>& assistant_screenshot) {
+  if (assistant::features::IsScreenContextQueryEnabled()) {
+    assistant_client::VoicelessOptions options;
+    options.is_user_initiated = true;
+
+    assistant_manager_internal_->SendTextQueryWithClientDiscourseContext(
+        kScreenContextQuery,
+        CreateContextProto(
+            AssistantBundle{assistant_extra_.get(), assistant_tree_.get()},
+            assistant_screenshot),
+        options);
+    return;
+  }
+
   std::vector<std::string> context_protos;
 
   // Screen context can have the assistant_extra and assistant_tree set to

chromeos/services/assistant/public/features.cc

@@ -98,6 +98,12 @@ const base::Feature kEnableTextQueriesWithClientDiscourseContext{
 const base::Feature kEnablePowerManager{"ChromeOSAssistantEnablePowerManager",
                                         base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables sending a screen context request ("What's on my screen?" and
+// metalayer selection) as a text query. This is as opposed to sending
+// the request as a contextual cards request.
+const base::Feature kScreenContextQuery{"ChromeOSAssistantScreenContextQuery",
+                                        base::FEATURE_DISABLED_BY_DEFAULT};
+
 const base::Feature kEnableMediaSessionIntegration{
     "AssistantEnableMediaSessionIntegration",
     base::FEATURE_DISABLED_BY_DEFAULT};
@@ -188,6 +194,10 @@ bool IsRoutinesEnabled() {
   return base::FeatureList::IsEnabled(kAssistantRoutines);
 }
 
+bool IsScreenContextQueryEnabled() {
+  return base::FeatureList::IsEnabled(kScreenContextQuery);
+}
+
 bool IsStereoAudioInputEnabled() {
   return base::FeatureList::IsEnabled(kEnableStereoAudioInput) ||
          // Audio eraser requires 2 channel input.

chromeos/services/assistant/public/features.h

@@ -137,6 +137,8 @@ bool IsResponseProcessingV2Enabled();
 
 COMPONENT_EXPORT(ASSISTANT_SERVICE_PUBLIC) bool IsRoutinesEnabled();
 
+COMPONENT_EXPORT(ASSISTANT_SERVICE_PUBLIC) bool IsScreenContextQueryEnabled();
+
 COMPONENT_EXPORT(ASSISTANT_SERVICE_PUBLIC) bool IsStereoAudioInputEnabled();
 
 COMPONENT_EXPORT(ASSISTANT_SERVICE_PUBLIC) bool IsWarmerWelcomeEnabled();