Create and pass shared-histogram-allocator from browser to renderer.

chrome/browser/metrics/subprocess_metrics_provider_unittest.cc

Index: chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
diff --git a/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc b/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..f60943b76b85531f63f9d0af18aba75209649cd4
--- /dev/null
+++ b/chrome/browser/metrics/subprocess_metrics_provider_unittest.cc
@@ -0,0 +1,211 @@
+// Copyright 2016 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 "chrome/browser/metrics/subprocess_metrics_provider.h"
+
+#include "base/memory/shared_memory.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/histogram_flattener.h"
+#include "base/metrics/histogram_snapshot_manager.h"
+#include "base/metrics/persistent_histogram_allocator.h"
+#include "base/metrics/persistent_memory_allocator.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+const uint32_t TEST_MEMORY_SIZE = 64 << 10;  // 64 KiB
+}  // namespace
+
+class HistogramFlattenerDeltaRecorder : public base::HistogramFlattener {

[grt (UTC plus 2), 2016/04/01 14:22:48]

nit: put this helper into the unnamed namespace

[bcwhite, 2016/04/01 16:50:26]

Done.

+ public:
+  HistogramFlattenerDeltaRecorder() {}
+
+  void RecordDelta(const base::HistogramBase& histogram,
+                   const base::HistogramSamples& snapshot) override {
+    recorded_delta_histogram_names_.push_back(histogram.histogram_name());
+  }
+
+  void InconsistencyDetected(
+      base::HistogramBase::Inconsistency problem) override {
+    ASSERT_TRUE(false);
+  }
+
+  void UniqueInconsistencyDetected(
+      base::HistogramBase::Inconsistency problem) override {
+    ASSERT_TRUE(false);
+  }
+
+  void InconsistencyDetectedInLoggedCount(int amount) override {
+    ASSERT_TRUE(false);
+  }
+
+  std::vector<std::string> GetRecordedDeltaHistogramNames() {
+    return recorded_delta_histogram_names_;
+  }
+
+ private:
+  std::vector<std::string> recorded_delta_histogram_names_;
+
+  DISALLOW_COPY_AND_ASSIGN(HistogramFlattenerDeltaRecorder);
+};
+
+class SubprocessMetricsProviderTest : public testing::Test {
+ protected:
+  SubprocessMetricsProviderTest() {}
+
+  void SetUp() override {

[grt (UTC plus 2), 2016/04/01 14:22:48]

nit: prefer the ctor/dtor pair over SetUp/TearDown when possible
(https://github.com/google/googletest/blob/master/googletest/docs/FAQ.md#shoul...).

[bcwhite, 2016/04/01 16:50:26]

Done.

+    // Get this first so it isn't created inside a persistent allocator.
+    base::PersistentHistogramAllocator::GetCreateHistogramResultHistogram();
+
+    // RecordHistogramSnapshots needs to becalled beause it uses a histogram
+    // macro which caches a pointer to a histogram. If not done before setting
+    // a persistent global allocator, then it would point into memory that
+    // will go away. The easiest way to call it is through an existing utility
+    // method.
+    GetSnapshotHistogramCount();
+
+    // Create some shared-memory to pass between global allocator and provider.
+    scoped_ptr<base::SharedMemory> shmem(new base::SharedMemory());
+    DCHECK(shmem->CreateAndMapAnonymous(TEST_MEMORY_SIZE));
+
+    // Keep a weak-pointer to the shared memory since it will be hidden once
+    // made part of the global histogram allocator.
+    shared_memory_ = shmem.get();
+
+    // Use the shared memory for all histograms created by this process.
+    base::PersistentHistogramAllocator::CreateGlobalAllocatorOnSharedMemory(
+        std::move(shmem), TEST_MEMORY_SIZE, 0, "");
+
+    // Enable metrics reporting by default.
+    provider_.OnRecordingEnabled();
+  }
+
+  void TearDown() override {
+    base::PersistentHistogramAllocator::ReleaseGlobalAllocatorForTesting();
+  }
+
+  SubprocessMetricsProvider* provider() { return &provider_; }
+
+  base::SharedMemory* shared_memory() { return shared_memory_; }
+
+  scoped_ptr<base::PersistentHistogramAllocator> GetDuplicateAllocator() {
+    base::SharedMemoryHandle memory_handle;
+    DCHECK(shared_memory_->ShareToProcess(base::GetCurrentProcessHandle(),
+                                          &memory_handle));
+
+    scoped_ptr<base::SharedMemory> shmem(
+        new base::SharedMemory(memory_handle, /*readonly=*/false));
+    DCHECK(shmem->Map(TEST_MEMORY_SIZE));
+
+    return make_scoped_ptr(new base::PersistentHistogramAllocator(
+        make_scoped_ptr(new base::SharedPersistentMemoryAllocator(
+            std::move(shmem), 0, "", false))));
+  }
+
+  size_t GetSnapshotHistogramCount() {
+    HistogramFlattenerDeltaRecorder flattener;
+    base::HistogramSnapshotManager snapshot_manager(&flattener);
+    snapshot_manager.StartDeltas();
+    provider_.RecordHistogramSnapshots(&snapshot_manager);
+    snapshot_manager.FinishDeltas();
+    return flattener.GetRecordedDeltaHistogramNames().size();
+  }
+
+  void EnableRecording() { provider_.OnRecordingEnabled(); }
+  void DisableRecording() { provider_.OnRecordingDisabled(); }
+
+  void RegisterSubprocessAllocator(
+      int id,
+      scoped_ptr<base::PersistentHistogramAllocator> allocator) {
+    provider_.RegisterSubprocessAllocator(id, std::move(allocator));
+  }
+
+  void DeregisterSubprocessAllocator(int id) {
+    provider_.DeregisterSubprocessAllocator(id);
+  }
+
+ private:
+  SubprocessMetricsProvider provider_;
+  base::SharedMemory* shared_memory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SubprocessMetricsProviderTest);
+};
+
+TEST_F(SubprocessMetricsProviderTest, SnapshotMetrics) {
+  base::HistogramBase* foo = base::Histogram::FactoryGet("foo", 1, 100, 10, 0);
+  base::HistogramBase* bar = base::Histogram::FactoryGet("bar", 1, 100, 10, 0);
+  foo->Add(42);
+  bar->Add(84);
+
+  // Register an allocator that duplicates the global allocator.
+  RegisterSubprocessAllocator(123, GetDuplicateAllocator());
+
+  // Recording should find the two histograms created in persistent memory.
+  EXPECT_EQ(2U, GetSnapshotHistogramCount());
+
+  // A second run should have nothing to produce.
+  EXPECT_EQ(0U, GetSnapshotHistogramCount());
+
+  // Create a new histogram and update existing ones. Should now report 3 items.
+  base::HistogramBase* baz = base::Histogram::FactoryGet("baz", 1, 100, 10, 0);
+  baz->Add(1969);
+  foo->Add(10);
+  bar->Add(20);
+  EXPECT_EQ(3U, GetSnapshotHistogramCount());
+
+  // Ensure that deregistering still keeps allocator around for final report.
+  foo->Add(10);
+  bar->Add(20);
+  DeregisterSubprocessAllocator(123);
+  EXPECT_EQ(2U, GetSnapshotHistogramCount());
+
+  // Further snapshots should be empty even if things have changed.
+  foo->Add(10);
+  bar->Add(20);
+  EXPECT_EQ(0U, GetSnapshotHistogramCount());
+}
+
+TEST_F(SubprocessMetricsProviderTest, EnableDisable) {
+  base::HistogramBase* foo = base::Histogram::FactoryGet("foo", 1, 100, 10, 0);
+  base::HistogramBase* bar = base::Histogram::FactoryGet("bar", 1, 100, 10, 0);
+
+  // Simulate some "normal" operation...
+  RegisterSubprocessAllocator(123, GetDuplicateAllocator());
+  foo->Add(42);
+  bar->Add(84);
+  EXPECT_EQ(2U, GetSnapshotHistogramCount());
+  foo->Add(42);
+  bar->Add(84);
+  EXPECT_EQ(2U, GetSnapshotHistogramCount());
+
+  // Ensure that disable/enable reporting won't affect "live" allocators.
+  DisableRecording();
+  EnableRecording();
+  foo->Add(42);
+  bar->Add(84);
+  EXPECT_EQ(2U, GetSnapshotHistogramCount());
+
+  // Ensure that allocators are released when reporting is disabled.
+  DisableRecording();
+  DeregisterSubprocessAllocator(123);
+  EnableRecording();
+  foo->Add(42);
+  bar->Add(84);
+  EXPECT_EQ(0U, GetSnapshotHistogramCount());
+
+  // Ensure that allocators added when reporting disabled will work if enabled.
+  DisableRecording();
+  RegisterSubprocessAllocator(123, GetDuplicateAllocator());
+  EnableRecording();
+  foo->Add(42);
+  bar->Add(84);
+  EXPECT_EQ(2U, GetSnapshotHistogramCount());
+
+  // Ensure that last-chance allocators are released if reporting is disabled.
+  DeregisterSubprocessAllocator(123);
+  DisableRecording();
+  EnableRecording();
+  foo->Add(42);
+  bar->Add(84);
+  EXPECT_EQ(0U, GetSnapshotHistogramCount());
+}