[tracing] Don't register tracing-related allocations.

base/trace_event/heap_profiler_allocation_context_tracker_unittest.cc

 // Copyright 2015 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 <stddef.h>
 
 #include <iterator>
 
 #include "base/memory/ref_counted.h"
 #include "base/pending_task.h"
@@ skipping 25 matching lines @@
     "      \"filter_predicate\": \"heap_profiler_predicate\","
     "      \"included_categories\": [\"*\"]"
     "    }"
     "  ]"
     "}";
 
 // Asserts that the fixed-size array |expected_backtrace| matches the backtrace
 // in |AllocationContextTracker::GetContextSnapshot|.
 template <size_t N>
 void AssertBacktraceEquals(const StackFrame(&expected_backtrace)[N]) {
-  AllocationContext ctx =
-      AllocationContextTracker::GetInstanceForCurrentThread()
-          ->GetContextSnapshot();
+  AllocationContext ctx;
+  ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                  ->GetContextSnapshot(&ctx));
 
   auto* actual = std::begin(ctx.backtrace.frames);
   auto* actual_bottom = actual + ctx.backtrace.frame_count;
   auto expected = std::begin(expected_backtrace);
   auto expected_bottom = std::end(expected_backtrace);
 
   // Note that this requires the pointers to be equal, this is not doing a deep
   // string comparison.
   for (; actual != actual_bottom && expected != expected_bottom;
        actual++, expected++)
     ASSERT_EQ(*expected, *actual);
 
   // Ensure that the height of the stacks is the same.
   ASSERT_EQ(actual, actual_bottom);
   ASSERT_EQ(expected, expected_bottom);
 }
 
 void AssertBacktraceContainsOnlyThreadName() {
   StackFrame t = StackFrame::FromThreadName(kThreadName);
-  AllocationContext ctx =
-      AllocationContextTracker::GetInstanceForCurrentThread()
-          ->GetContextSnapshot();
+  AllocationContext ctx;
+  ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                  ->GetContextSnapshot(&ctx));
 
   ASSERT_EQ(1u, ctx.backtrace.frame_count);
   ASSERT_EQ(t, ctx.backtrace.frames[0]);
 }
 
 class AllocationContextTrackerTest : public testing::Test {
  public:
   void SetUp() override {
     AllocationContextTracker::SetCaptureMode(
         AllocationContextTracker::CaptureMode::PSEUDO_STACK);
@@ skipping 155 matching lines @@
   TRACE_EVENT0("Testing", kCupcake);
   TRACE_EVENT0("Testing", kCupcake);
 
   TRACE_EVENT0("Testing", kCupcake);
   TRACE_EVENT0("Testing", kDonut);
   TRACE_EVENT0("Testing", kEclair);
   TRACE_EVENT0("Testing", kFroyo);
 
   {
     TRACE_EVENT0("Testing", kGingerbread);
-    AllocationContext ctx =
-        AllocationContextTracker::GetInstanceForCurrentThread()
-            ->GetContextSnapshot();
+    AllocationContext ctx;
+    ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                    ->GetContextSnapshot(&ctx));
 
     // The pseudo stack relies on pointer equality, not deep string comparisons.
     ASSERT_EQ(t, ctx.backtrace.frames[0]);
     ASSERT_EQ(c, ctx.backtrace.frames[1]);
     ASSERT_EQ(f, ctx.backtrace.frames[11]);
   }
 
   {
-    AllocationContext ctx =
-        AllocationContextTracker::GetInstanceForCurrentThread()
-            ->GetContextSnapshot();
+    AllocationContext ctx;
+    ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                    ->GetContextSnapshot(&ctx));
     ASSERT_EQ(t, ctx.backtrace.frames[0]);
     ASSERT_EQ(c, ctx.backtrace.frames[1]);
     ASSERT_EQ(f, ctx.backtrace.frames[11]);
   }
 }
 
 TEST_F(AllocationContextTrackerTest, TrackCategoryName) {
   const char kContext1[] = "context1";
   const char kContext2[] = "context2";
   {
     // The context from the scoped task event should be used as type name.
     TRACE_HEAP_PROFILER_API_SCOPED_TASK_EXECUTION event1(kContext1);
-    AllocationContext ctx1 =
-        AllocationContextTracker::GetInstanceForCurrentThread()
-            ->GetContextSnapshot();
+    AllocationContext ctx1;
+    ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                    ->GetContextSnapshot(&ctx1));
     ASSERT_EQ(kContext1, ctx1.type_name);
 
     // In case of nested events, the last event's context should be used.
     TRACE_HEAP_PROFILER_API_SCOPED_TASK_EXECUTION event2(kContext2);
-    AllocationContext ctx2 =
-        AllocationContextTracker::GetInstanceForCurrentThread()
-            ->GetContextSnapshot();
+    AllocationContext ctx2;
+    ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                    ->GetContextSnapshot(&ctx2));
     ASSERT_EQ(kContext2, ctx2.type_name);
   }
 
   {
     // Type should be category name of the last seen trace event.
     TRACE_EVENT0("Testing", kCupcake);
-    AllocationContext ctx1 =
-        AllocationContextTracker::GetInstanceForCurrentThread()
-            ->GetContextSnapshot();
+    AllocationContext ctx1;
+    ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                    ->GetContextSnapshot(&ctx1));
     ASSERT_EQ("Testing", std::string(ctx1.type_name));
 
     TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("Testing"), kCupcake);
-    AllocationContext ctx2 =
-        AllocationContextTracker::GetInstanceForCurrentThread()
-            ->GetContextSnapshot();
+    AllocationContext ctx2;
+    ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                    ->GetContextSnapshot(&ctx2));
     ASSERT_EQ(TRACE_DISABLED_BY_DEFAULT("Testing"),
               std::string(ctx2.type_name));
   }
 
   // Type should be nullptr without task event.
-  AllocationContext ctx =
-      AllocationContextTracker::GetInstanceForCurrentThread()
-          ->GetContextSnapshot();
+  AllocationContext ctx;
+  ASSERT_TRUE(AllocationContextTracker::GetInstanceForCurrentThread()
+                  ->GetContextSnapshot(&ctx));
   ASSERT_FALSE(ctx.type_name);
 }
 
 TEST_F(AllocationContextTrackerTest, IgnoreAllocationTest) {
   TRACE_EVENT0("Testing", kCupcake);
   TRACE_EVENT0("Testing", kDonut);
   HEAP_PROFILER_SCOPED_IGNORE;
-  AllocationContext ctx =
-      AllocationContextTracker::GetInstanceForCurrentThread()
-          ->GetContextSnapshot();
-  const StringPiece kTracingOverhead("tracing_overhead");
-  ASSERT_EQ(kTracingOverhead,
-            static_cast<const char*>(ctx.backtrace.frames[0].value));
-  ASSERT_EQ(1u, ctx.backtrace.frame_count);
+  AllocationContext ctx;
+  ASSERT_FALSE(AllocationContextTracker::GetInstanceForCurrentThread()
+                   ->GetContextSnapshot(&ctx));
 }
 
 }  // namespace trace_event
 }  // namespace base