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 6567ba9b4220a28ce58cac63592d53bc54e3c3dc..f9a7e490fdeee7a9924f1b26ac5484223a80c6ed 100644
--- a/extensions/common/feature_switch.cc
+++ b/extensions/common/feature_switch.cc
@@ -20,6 +20,8 @@ namespace {
 const char kLoadMediaRouterComponentExtensionFlag[] =
     "load-media-router-component-extension";
 
+const char kYieldBetweenContentScriptRuns[] = "YieldBetweenContentScriptRuns";
+
 class CommonSwitches {
  public:
   CommonSwitches()
@@ -54,7 +56,11 @@ 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,
+            kYieldBetweenContentScriptRuns,

[Devlin, 2017/03/10 03:18:45]

We should rename this to be kYieldBetweenContentScriptRunsFieldTrial or similar
to differentiate.

[Kunihiko Sakamoto, 2017/03/10 07:07:28]

Done.

+            FeatureSwitch::DEFAULT_DISABLED) {
   }
 
   FeatureSwitch force_dev_mode_highlighting;
@@ -71,6 +77,7 @@ 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> g_common_switches =
@@ -108,6 +115,9 @@ 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)
@@ -148,12 +158,18 @@ FeatureSwitch::FeatureSwitch(const base::CommandLine* command_line,
       switch_name_(switch_name),
       field_trial_name_(field_trial_name),
       default_value_(default_value == DEFAULT_ENABLED),
-      override_value_(OVERRIDE_NONE) {}
+      override_value_(OVERRIDE_NONE),
+      cached_value_(NOT_CACHED) {}
 
 bool FeatureSwitch::IsEnabled() const {
   if (override_value_ != OVERRIDE_NONE)
     return override_value_ == OVERRIDE_ENABLED;
+  if (cached_value_ == NOT_CACHED)
+    cached_value_ = ComputeValue() ? CACHED_ENABLED : CACHED_DISABLED;
+  return cached_value_ == CACHED_ENABLED;
+}
 
+bool FeatureSwitch::ComputeValue() const {
   if (!switch_name_)
     return default_value_;