Update load start time

Add a V8 API to update load start time for RAIL PERFORMANCE_LOAD mode

Bug: v8:10947

Change-Id: If86a815f8974b47a6f4ba82c3661c21b73f39553
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2423403
Auto-Submit: Hong Zheng <hong.zheng@intel.com>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73393}

include/v8.h

@@ -9323,6 +9323,11 @@ class V8_EXPORT Isolate {
    */
   void SetRAILMode(RAILMode rail_mode);
 
+  /**
+   * Update load start time of the RAIL mode
+   */
+  void UpdateLoadStartTime();
+
   /**
    * Optional notification to tell V8 the current isolate is used for debugging
    * and requires higher heap limit.

src/api/api.cc

@@ -8761,6 +8761,11 @@ void Isolate::SetRAILMode(RAILMode rail_mode) {
   return isolate->SetRAILMode(rail_mode);
 }
 
+void Isolate::UpdateLoadStartTime() {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  isolate->UpdateLoadStartTime();
+}
+
 void Isolate::IncreaseHeapLimitForDebugging() {
   // No-op.
 }

src/execution/isolate.cc

@@ -4575,6 +4575,11 @@ double Isolate::LoadStartTimeMs() {
   return load_start_time_ms_;
 }
 
+void Isolate::UpdateLoadStartTime() {
+  base::MutexGuard guard(&rail_mutex_);
+  load_start_time_ms_ = heap()->MonotonicallyIncreasingTimeInMs();
+}
+
 void Isolate::SetRAILMode(RAILMode rail_mode) {
   RAILMode old_rail_mode = rail_mode_.load();
   if (old_rail_mode != PERFORMANCE_LOAD && rail_mode == PERFORMANCE_LOAD) {

src/execution/isolate.h

@@ -1601,6 +1601,8 @@ class V8_EXPORT_PRIVATE Isolate final : private HiddenFactory {
 
   double LoadStartTimeMs();
 
+  void UpdateLoadStartTime();
+
   void IsolateInForegroundNotification();
 
   void IsolateInBackgroundNotification();