Split content script injections into multiple tasks

extensions/common/feature_switch.h

Index: extensions/common/feature_switch.h
diff --git a/extensions/common/feature_switch.h b/extensions/common/feature_switch.h
index 6e2f8e7abad26aea46e520971f32ce80d79f2f54..df10bd5db56dd84547bf65e76d334fe055fe28f4 100644
--- a/extensions/common/feature_switch.h
+++ b/extensions/common/feature_switch.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/macros.h"
+#include "base/optional.h"
 
 namespace base {
 class CommandLine;
@@ -41,6 +42,7 @@ class FeatureSwitch {
   static FeatureSwitch* trace_app_source();
   static FeatureSwitch* load_media_router_component_extension();
   static FeatureSwitch* native_crx_bindings();
+  static FeatureSwitch* yield_between_content_script_runs();
 
   enum DefaultValue {
     DEFAULT_ENABLED,
@@ -88,12 +90,14 @@ class FeatureSwitch {
  private:
   std::string GetLegacyEnableFlag() const;
   std::string GetLegacyDisableFlag() const;
+  bool ComputeValue() const;
 
   const base::CommandLine* command_line_;
   const char* switch_name_;
   const char* field_trial_name_;
   bool default_value_;
   OverrideValue override_value_;
+  mutable base::Optional<bool> cached_value_;
 
   DISALLOW_COPY_AND_ASSIGN(FeatureSwitch);
 };