Make sure CPU profiler collects a sample on start.

src/cpu-profiler.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "v8.h"
 
 #include "cpu-profiler-inl.h"
 
 #include "compiler.h"
 #include "frames-inl.h"
@@ skipping 400 matching lines @@
   }
 }
 
 
 void CpuProfiler::StartProfiling(String* title, bool record_samples) {
   StartProfiling(profiles_->GetName(title), record_samples);
 }
 
 
 void CpuProfiler::StartProcessorIfNotStarted() {
-  if (processor_ == NULL) {
-    Logger* logger = isolate_->logger();
-    // Disable logging when using the new implementation.
-    saved_is_logging_ = logger->is_logging_;
-    logger->is_logging_ = false;
-    generator_ = new ProfileGenerator(profiles_);
-    Sampler* sampler = logger->sampler();
-    processor_ = new ProfilerEventsProcessor(
-        generator_, sampler, sampling_interval_);
-    is_profiling_ = true;
-    // Enumerate stuff we already have in the heap.
-    ASSERT(isolate_->heap()->HasBeenSetUp());
-    if (!FLAG_prof_browser_mode) {
-      logger->LogCodeObjects();
-    }
-    logger->LogCompiledFunctions();
-    logger->LogAccessorCallbacks();
-    LogBuiltins();
-    // Enable stack sampling.
-    sampler->SetHasProcessingThread(true);
-    sampler->IncreaseProfilingDepth();
+  if (processor_ != NULL) {
     processor_->AddCurrentStack(isolate_);
-    processor_->StartSynchronously();
+    return;
   }
+  Logger* logger = isolate_->logger();
+  // Disable logging when using the new implementation.
+  saved_is_logging_ = logger->is_logging_;
+  logger->is_logging_ = false;
+  generator_ = new ProfileGenerator(profiles_);
+  Sampler* sampler = logger->sampler();
+  processor_ = new ProfilerEventsProcessor(
+      generator_, sampler, sampling_interval_);
+  is_profiling_ = true;
+  // Enumerate stuff we already have in the heap.
+  ASSERT(isolate_->heap()->HasBeenSetUp());
+  if (!FLAG_prof_browser_mode) {
+    logger->LogCodeObjects();
+  }
+  logger->LogCompiledFunctions();
+  logger->LogAccessorCallbacks();
+  LogBuiltins();
+  // Enable stack sampling.
+  sampler->SetHasProcessingThread(true);
+  sampler->IncreaseProfilingDepth();
+  processor_->AddCurrentStack(isolate_);
+  processor_->StartSynchronously();
 }
 
 
 CpuProfile* CpuProfiler::StopProfiling(const char* title) {
   if (!is_profiling_) return NULL;
   StopProcessorIfLastProfile(title);
   CpuProfile* result = profiles_->StopProfiling(title);
   if (result != NULL) {
     result->Print();
   }
@@ skipping 37 matching lines @@
     ReportBuiltinEventRecord* rec = &evt_rec.ReportBuiltinEventRecord_;
     Builtins::Name id = static_cast<Builtins::Name>(i);
     rec->start = builtins->builtin(id)->address();
     rec->builtin_id = id;
     processor_->Enqueue(evt_rec);
   }
 }
 
 
 } }  // namespace v8::internal