[heap profiler] Support allocation sizes > 2GB in memlog.

BUG=1002170

Change-Id: I81953154de3326f84e2a240c0ed879bec6ad91cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1793358
Commit-Queue: Alexei Filippov <alph@chromium.org>
Reviewed-by: Erik Chen <erikchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695029}

components/services/heap_profiling/json_exporter.cc

@@ -234,10 +234,12 @@ base::Value BuildAllocations(const AllocationMap& allocations,
 
   for (const auto& alloc : allocations) {
     int allocator = static_cast<int>(alloc.first.allocator);
+    // We use double to store size and count, as it can precisely represent
+    // values up to 2^52 ~ 4.5 petabytes.
     counts[allocator].push_back(
-        base::Value(static_cast<int>(alloc.second.count)));
+        base::Value(static_cast<double>(alloc.second.count)));
     sizes[allocator].push_back(
-        base::Value(static_cast<int>(alloc.second.size)));
+        base::Value(static_cast<double>(alloc.second.size)));
     types[allocator].push_back(base::Value(alloc.first.context_id));
     nodes[allocator].push_back(base::Value(alloc_to_node_id.at(&alloc.first)));
   }
@@ -300,7 +302,9 @@ std::string ExportMemoryMapsAndV2StackTraceToJSON(ExportParams* params) {
   result.SetKey("heaps_v2", std::move(heaps_v2));
 
   std::string result_json;
-  bool ok = base::JSONWriter::Write(result, &result_json);
+  bool ok = base::JSONWriter::WriteWithOptions(
+      result, base::JSONWriter::OPTIONS_OMIT_DOUBLE_TYPE_PRESERVATION,
+      &result_json);
   DCHECK(ok);
   return result_json;
 }

components/services/heap_profiling/json_exporter_unittest.cc

@@ -421,4 +421,43 @@ TEST(ProfilingJsonExporterTest, Context) {
   ASSERT_TRUE(found_no_context);
 }
 
+#if defined(ARCH_CPU_64_BITS)
+TEST(ProfilingJsonExporterTest, LargeAllocation) {
+  std::vector<Address> stack1{Address(0x5678), Address(0x1234)};
+  AllocationMap allocs;
+  InsertAllocation(&allocs, AllocatorType::kMalloc,
+                   static_cast<size_t>(0x9876543210ul), stack1, 0);
+
+  ExportParams params;
+  params.allocs = std::move(allocs);
+  std::string json = ExportMemoryMapsAndV2StackTraceToJSON(&params);
+
+  // JSON should parse.
+  base::JSONReader json_reader(base::JSON_PARSE_RFC);
+  base::Optional<base::Value> result = json_reader.ReadToValue(json);
+  ASSERT_TRUE(result.has_value()) << json_reader.GetErrorMessage();
+
+  // Validate the allocators summary.
+  const base::Value* malloc_summary =
+      result.value().FindPath({"allocators", "malloc"});
+  ASSERT_TRUE(malloc_summary);
+  const base::Value* malloc_size =
+      malloc_summary->FindPath({"attrs", "size", "value"});
+  ASSERT_TRUE(malloc_size);
+  EXPECT_EQ("9876543210", malloc_size->GetString());
+  const base::Value* malloc_virtual_size =
+      malloc_summary->FindPath({"attrs", "virtual_size", "value"});
+  ASSERT_TRUE(malloc_virtual_size);
+  EXPECT_EQ("9876543210", malloc_virtual_size->GetString());
+
+  // Validate allocators details.
+  // heaps_v2.allocators.malloc.sizes.reduce((a,s)=>a+s,0).
+  const base::Value* malloc =
+      result.value().FindPath({"heaps_v2", "allocators", "malloc"});
+  const base::Value* malloc_sizes = malloc->FindKey("sizes");
+  EXPECT_EQ(1u, malloc_sizes->GetList().size());
+  EXPECT_EQ(0x9876543210ul, malloc_sizes->GetList()[0].GetDouble());
+}
+#endif
+
 }  // namespace heap_profiling