[idle] Implement kill switch for IdleDetection

IdleDetection allows sites to observe user idle status. Before launching
this feature, we want to add a kill switch that can be set from
server side that lets us turn off the feature in case where there is a
security or privacy problem.


Bug: 947707
Change-Id: Ic44fcaf6ed2ce5f5ae5026fc8040be1b51dac26f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1548035Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Ayu Ishii <ayui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#649192}

content/child/runtime_features.cc

@@ -481,6 +481,9 @@ void SetIndividualRuntimeFeatures(
   WebRuntimeFeatures::EnableSignedExchangeSubresourcePrefetch(
       base::FeatureList::IsEnabled(
           features::kSignedExchangeSubresourcePrefetch));
+
+  if (!base::FeatureList::IsEnabled(features::kIdleDetection))
+    WebRuntimeFeatures::EnableIdleDetection(false);
 }
 
 }  // namespace

content/public/common/content_features.cc

@@ -188,6 +188,12 @@ const base::Feature kHeapCompaction{"HeapCompaction",
 const base::Feature kHistoryManipulationIntervention{
     "HistoryManipulationIntervention", base::FEATURE_ENABLED_BY_DEFAULT};
 
+// This is intended as a kill switch for the Idle Detection feature. To enable
+// this feature,the experimental web platform features flag should be set,
+// or the site should obtain an Origin Trial token.
+const base::Feature kIdleDetection{"IdleDetection",
+                                   base::FEATURE_ENABLED_BY_DEFAULT};
+
 // This flag is used to set field parameters to choose predictor we use when
 // kResamplingInputEvents is disabled. It's used for gatherig accuracy metrics
 // on finch and also for choosing predictor type for predictedEvents API without

content/public/common/content_features.h

@@ -51,6 +51,7 @@ CONTENT_EXPORT extern const base::Feature kFreezeFramesOnVisibility;
 CONTENT_EXPORT extern const base::Feature kGuestViewCrossProcessFrames;
 CONTENT_EXPORT extern const base::Feature kHeapCompaction;
 CONTENT_EXPORT extern const base::Feature kHistoryManipulationIntervention;
+CONTENT_EXPORT extern const base::Feature kIdleDetection;
 CONTENT_EXPORT extern const base::Feature kInputPredictorTypeChoice;
 CONTENT_EXPORT extern const base::Feature kIsolateOrigins;
 CONTENT_EXPORT extern const char kIsolateOriginsFieldTrialParamName[];

third_party/blink/public/platform/web_runtime_features.h

@@ -234,6 +234,7 @@ class WebRuntimeFeatures {
   BLINK_PLATFORM_EXPORT static void EnableHTMLImports(bool);
   BLINK_PLATFORM_EXPORT static void EnableSignedExchangeSubresourcePrefetch(
       bool);
+  BLINK_PLATFORM_EXPORT static void EnableIdleDetection(bool);
 
  private:
   WebRuntimeFeatures();

third_party/blink/renderer/platform/exported/web_runtime_features.cc

@@ -648,4 +648,8 @@ void WebRuntimeFeatures::EnableSignedExchangeSubresourcePrefetch(bool enable) {
   RuntimeEnabledFeatures::SetSignedExchangeSubresourcePrefetchEnabled(enable);
 }
 
+void WebRuntimeFeatures::EnableIdleDetection(bool enable) {
+  RuntimeEnabledFeatures::SetIdleDetectionEnabled(enable);
+}
+
 }  // namespace blink