Reland of [tracing] Add heap profiler perftests.

> Reason for revert:
> This broke Win 64:
> https://build.chromium.org/p/chromium.win/buildstatus?builder=Win%20x64%20Builder%20%28dbg%29&number=56316
>
> Original issue's description:
> > [tracing] Add heap profiler perftests.
> >
> > This CL creates a generic place for heap profiler perftests, and adds
> > couple of stack frame deduplicator related perftests.
> >
> > BUG=739378
> >
> > Review-Url: https://codereview.chromium.org/2976843002
> > Cr-Commit-Position: refs/heads/master@{#486544}
> > Committed: https://chromium.googlesource.com/chromium/src/+/f43d398eac5c9d4c2bccda6d2630d108bbed1c99
>
> TBR=primiano@chromium.org,dskiba@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=739378
>
> Review-Url: https://codereview.chromium.org/2981833002
> Cr-Commit-Position: refs/heads/master@{#486555}

TBR=primiano@chromium.org

BUG=739378

Review-Url: https://codereview.chromium.org/2975133004
Cr-Commit-Position: refs/heads/master@{#486744}

components/tracing/BUILD.gn

@@ -122,6 +122,7 @@ source_set("unit_tests") {
 
 test("tracing_perftests") {
   sources = [
+    "test/heap_profiler_perftest.cc",
     "test/perf_test_helpers.cc",
     "test/perf_test_helpers.h",
     "test/trace_event_perftest.cc",

components/tracing/test/heap_profiler_perftest.cc

+// Copyright 2017 The Chromium 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 <algorithm>
+#include <iterator>
+#include <vector>
+
+#include "base/memory/ptr_util.h"
+#include "base/strings/stringprintf.h"
+#include "base/time/time.h"
+#include "base/trace_event/heap_profiler_stack_frame_deduplicator.h"
+#include "base/trace_event/heap_profiler_string_deduplicator.h"
+#include "base/trace_event/trace_event_argument.h"
+#include "perf_test_helpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace tracing {
+namespace {
+
+using namespace base::trace_event;
+
+class HeapProfilerPerfTest : public testing::Test {
+ protected:
+  struct StackFrameVariations {
+    size_t skew;
+    std::vector<StackFrame> values;
+  };
+  using BacktraceVariations = std::vector<StackFrameVariations>;
+
+  BacktraceVariations GetRandomBacktraceVariations() {
+    struct VariationSpec {
+      size_t value_count;  // number of unique frames
+      size_t skew;         // see GetSkewedRandom()
+      size_t length;       // number of backtrace levels covered
+    };
+    static const VariationSpec specs[] = {
+        // These values give realistic insertion pattern with 60% hit count.
+        {100, 90, Backtrace::kMaxFrameCount - 5},
+        {10, 5, 5}};
+
+    BacktraceVariations backtrace_variations;
+    const VariationSpec* spec = std::begin(specs);
+    size_t spec_end_depth = spec->length;
+    for (size_t depth = 0; depth != Backtrace::kMaxFrameCount; ++depth) {
+      if (depth == spec_end_depth) {
+        if (spec != std::end(specs) - 1) {
+          spec++;
+          spec_end_depth = depth + spec->length;
+        } else {
+          spec_end_depth = Backtrace::kMaxFrameCount;
+        }
+      }
+      backtrace_variations.push_back({spec->skew});
+      auto& frame_variations = backtrace_variations.back();
+      for (size_t v = 0; v != spec->value_count; ++v) {
+        uintptr_t pc = static_cast<uintptr_t>(GetRandom64());
+        frame_variations.values.push_back(
+            StackFrame::FromProgramCounter(reinterpret_cast<void*>(pc)));
+      }
+    }
+
+    return backtrace_variations;
+  }
+
+  size_t InsertRandomBacktraces(StackFrameDeduplicator* deduplicator,
+                                const BacktraceVariations& backtrace_variations,
+                                size_t max_frame_count) {
+    size_t insert_count = 0;
+    while (true) {
+      insert_count++;
+      Backtrace backtrace = RandomBacktrace(backtrace_variations);
+      deduplicator->Insert(backtrace.frames,
+                           backtrace.frames + backtrace.frame_count);
+      size_t frame_count = deduplicator->end() - deduplicator->begin();
+      if (frame_count > max_frame_count) {
+        break;
+      }
+    }
+    return insert_count;
+  }
+
+ private:
+  uint32_t GetRandom32() {
+    random_seed_ = random_seed_ * 1664525 + 1013904223;
+    return random_seed_;
+  }
+
+  uint64_t GetRandom64() {
+    uint64_t rnd = GetRandom32();
+    return (rnd << 32) | GetRandom32();
+  }
+
+  // Returns random number in range [0, max).
+  uint32_t GetRandom32(uint32_t max) {
+    uint64_t rnd = GetRandom32();
+    return static_cast<uint32_t>((rnd * max) >> 32);
+  }
+
+  // In 1/skew cases returns random value in range [0, max), in all
+  // other cases returns value in range [0, max/skew). The average value
+  // ends up being (2*skew - 1) / (2*skew^2) * max.
+  uint32_t GetSkewedRandom(uint32_t max, uint32_t skew) {
+    if (GetRandom32(skew) != (skew - 1)) {
+      max /= skew;
+    }
+    return GetRandom32(max);
+  }
+
+  Backtrace RandomBacktrace(const BacktraceVariations& backtrace_variations) {
+    Backtrace backtrace;
+    backtrace.frame_count = Backtrace::kMaxFrameCount;
+    for (size_t depth = 0; depth != backtrace.frame_count; ++depth) {
+      const auto& frame_variations = backtrace_variations[depth];
+      size_t value_index =
+          GetSkewedRandom(static_cast<uint32_t>(frame_variations.values.size()),
+                          static_cast<uint32_t>(frame_variations.skew));
+      backtrace.frames[depth] = frame_variations.values[value_index];
+    }
+    return backtrace;
+  }
+
+ private:
+  uint32_t random_seed_ = 777;
+};
+
+TEST_F(HeapProfilerPerfTest, DeduplicateStackFrames) {
+  StringDeduplicator string_deduplicator;
+  StackFrameDeduplicator deduplicator(&string_deduplicator);
+
+  auto variations = GetRandomBacktraceVariations();
+
+  {
+    ScopedStopwatch stopwatch("time_to_insert");
+    InsertRandomBacktraces(&deduplicator, variations, 1000000);
+  }
+}
+
+TEST_F(HeapProfilerPerfTest, AppendStackFramesAsTraceFormat) {
+  StringDeduplicator string_deduplicator;
+  StackFrameDeduplicator deduplicator(&string_deduplicator);
+
+  auto variations = GetRandomBacktraceVariations();
+  InsertRandomBacktraces(&deduplicator, variations, 1000000);
+
+  auto traced_value = base::MakeUnique<TracedValue>();
+  traced_value->BeginArray("nodes");
+  deduplicator.SerializeIncrementally(traced_value.get());
+  traced_value->EndArray();
+
+  {
+    ScopedStopwatch stopwatch("time_to_append");
+    std::string json;
+    traced_value->AppendAsTraceFormat(&json);
+  }
+}
+
+}  // namespace
+}  // namespace tracing