Split content script injections into multiple tasks

extensions/common/feature_switch.cc

Index: extensions/common/feature_switch.cc
diff --git a/extensions/common/feature_switch.cc b/extensions/common/feature_switch.cc
index 10863b271a059eeb4c7a05c347de8b76710e1dfb..5868f02869bfc064bd3bc90e09f2773ee258d350 100644
--- a/extensions/common/feature_switch.cc
+++ b/extensions/common/feature_switch.cc
@@ -20,6 +20,9 @@ namespace {
 const char kLoadMediaRouterComponentExtensionFlag[] =
     "load-media-router-component-extension";
 
+const char kYieldBetweenContentScriptRunsFieldTrial[] =
+    "YieldBetweenContentScriptRuns";
+
 class CommonSwitches {
  public:
   CommonSwitches()
@@ -54,7 +57,11 @@ class CommonSwitches {
             FeatureSwitch::DEFAULT_DISABLED),
 #endif  // defined(GOOGLE_CHROME_BUILD)
         native_crx_bindings(switches::kNativeCrxBindings,
-                            FeatureSwitch::DEFAULT_DISABLED) {
+                            FeatureSwitch::DEFAULT_DISABLED),
+        yield_between_content_script_runs(
+            switches::kYieldBetweenContentScriptRuns,
+            kYieldBetweenContentScriptRunsFieldTrial,
+            FeatureSwitch::DEFAULT_DISABLED) {
   }
 
   FeatureSwitch force_dev_mode_highlighting;
@@ -71,6 +78,7 @@ class CommonSwitches {
   FeatureSwitch trace_app_source;
   FeatureSwitch load_media_router_component_extension;
   FeatureSwitch native_crx_bindings;
+  FeatureSwitch yield_between_content_script_runs;
 };
 
 base::LazyInstance<CommonSwitches>::DestructorAtExit g_common_switches =
@@ -108,6 +116,9 @@ FeatureSwitch* FeatureSwitch::load_media_router_component_extension() {
 FeatureSwitch* FeatureSwitch::native_crx_bindings() {
   return &g_common_switches.Get().native_crx_bindings;
 }
+FeatureSwitch* FeatureSwitch::yield_between_content_script_runs() {
+  return &g_common_switches.Get().yield_between_content_script_runs;
+}
 
 FeatureSwitch::ScopedOverride::ScopedOverride(FeatureSwitch* feature,
                                               bool override_value)
@@ -153,7 +164,12 @@ FeatureSwitch::FeatureSwitch(const base::CommandLine* command_line,
 bool FeatureSwitch::IsEnabled() const {
   if (override_value_ != OVERRIDE_NONE)
     return override_value_ == OVERRIDE_ENABLED;
+  if (!cached_value_.has_value())
+    cached_value_ = ComputeValue();
+  return cached_value_.value();
+}
 
+bool FeatureSwitch::ComputeValue() const {
   if (!switch_name_)
     return default_value_;