disallow left-trim fast path when sampling heap profiler is active

test/cctest/test-heap-profiler.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3022 matching lines @@
   v8::base::SmartPointer<v8::AllocationProfile> profile(
       heap_profiler->GetAllocationProfile());
   CHECK(!profile.is_empty());
   const char* names[] = {"(V8 API)"};
   auto node = FindAllocationProfileNode(
       *profile, Vector<const char*>(names, arraysize(names)));
   CHECK(node);
 
   heap_profiler->StopSamplingHeapProfiler();
 }
+
+TEST(SamplingHeapProfilerLeftTrimming) {
+  v8::HandleScope scope(v8::Isolate::GetCurrent());
+  LocalContext env;
+  v8::HeapProfiler* heap_profiler = env->GetIsolate()->GetHeapProfiler();
+
+  // Suppress randomness to avoid flakiness in tests.
+  v8::internal::FLAG_sampling_heap_profiler_suppress_randomness = true;
+
+  heap_profiler->StartSamplingHeapProfiler(64);
+
+  CompileRun(
+      "for (var j = 0; j < 30000; ++j) {\n"
+      "  var a = [];\n"
+      "  for (var i = 0; i < 5; ++i)\n"
+      "      a[i] = i;\n"
+      "  for (var i = 0; i < 3; ++i)\n"
+      "      a.shift();\n"
+      "}\n");
+  // Should not crash.

[Hannes Payer (out of office), 2016/04/13 13:32:29]

Don't you need to call GC to crash? Why does it crash right now?

+
+  heap_profiler->StopSamplingHeapProfiler();
+}