Add HeapCompaction FeatureList flag

Adds HeapCompaction as a FeatureList flag so it can be enabled from a Finch experiment.

BUG=678923

Review-Url: https://codereview.chromium.org/2624693002
Cr-Commit-Position: refs/heads/master@{#443210}

content/child/runtime_features.cc

@@ -293,6 +293,9 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
       base::FeatureList::IsEnabled(
           features::kExpensiveBackgroundTimerThrottling));
 
+  if (base::FeatureList::IsEnabled(features::kHeapCompaction))
+    WebRuntimeFeatures::enableHeapCompaction(true);
+
   WebRuntimeFeatures::enableRenderingPipelineThrottling(
     base::FeatureList::IsEnabled(features::kRenderingPipelineThrottling));
 

content/public/common/content_features.cc

@@ -105,6 +105,10 @@ const base::Feature kGenericSensor{"GenericSensor",
 const base::Feature kGuestViewCrossProcessFrames{
     "GuestViewCrossProcessFrames", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables BlinkGC heap compaction.
+const base::Feature kHeapCompaction{"HeapCompaction",
+                                     base::FEATURE_DISABLED_BY_DEFAULT};
+
 // Enables lazily parsing css properties for performance.
 const base::Feature kLazyParseCSS{"LazyParseCSS",
                                   base::FEATURE_DISABLED_BY_DEFAULT};

content/public/common/content_features.h

@@ -35,6 +35,7 @@ CONTENT_EXPORT extern const base::Feature
 CONTENT_EXPORT extern const base::Feature kGamepadExtensions;
 CONTENT_EXPORT extern const base::Feature kGenericSensor;
 CONTENT_EXPORT extern const base::Feature kGuestViewCrossProcessFrames;
+CONTENT_EXPORT extern const base::Feature kHeapCompaction;
 CONTENT_EXPORT extern const base::Feature kLazyParseCSS;
 CONTENT_EXPORT extern const base::Feature kMediaDocumentDownloadButton;
 CONTENT_EXPORT extern const base::Feature kMemoryCoordinator;

third_party/WebKit/Source/web/WebRuntimeFeatures.cpp

@@ -150,6 +150,10 @@ void WebRuntimeFeatures::enableGenericSensor(bool enable) {
   RuntimeEnabledFeatures::setSensorEnabled(enable);
 }
 
+void WebRuntimeFeatures::enableHeapCompaction(bool enable) {
+  RuntimeEnabledFeatures::setHeapCompactionEnabled(enable);
+}
+
 void WebRuntimeFeatures::enableInputMultipleFieldsUI(bool enable) {
   RuntimeEnabledFeatures::setInputMultipleFieldsUIEnabled(enable);
 }

third_party/WebKit/public/web/WebRuntimeFeatures.h

@@ -84,6 +84,7 @@ class WebRuntimeFeatures {
   BLINK_EXPORT static void enableFileSystem(bool);
   BLINK_EXPORT static void enableGamepadExtensions(bool);
   BLINK_EXPORT static void enableGenericSensor(bool);
+  BLINK_EXPORT static void enableHeapCompaction(bool);
   BLINK_EXPORT static void enableInputMultipleFieldsUI(bool);
   BLINK_EXPORT static void enableLazyParseCSS(bool);
   BLINK_EXPORT static void enableMediaCapture(bool);