[tracing] Smaps provider uses fscanf instead of istream

base/trace_event/process_memory_maps_dump_provider_unittest.cc

Index: base/trace_event/process_memory_maps_dump_provider_unittest.cc
diff --git a/base/trace_event/process_memory_maps_dump_provider_unittest.cc b/base/trace_event/process_memory_maps_dump_provider_unittest.cc
index f951a09fb8a2aaf84a290a96ece8bf0db26a3518..d9b0832a6e065f335fc289fa0e425cc9db9bc43f 100644
--- a/base/trace_event/process_memory_maps_dump_provider_unittest.cc
+++ b/base/trace_event/process_memory_maps_dump_provider_unittest.cc
@@ -4,9 +4,9 @@
 
 #include "base/trace_event/process_memory_maps_dump_provider.h"
 
-#include <fstream>
-#include <sstream>
+#include <fcntl.h>
 
+#include "base/files/file_util.h"
 #include "base/trace_event/process_memory_dump.h"
 #include "base/trace_event/process_memory_maps.h"
 #include "base/trace_event/trace_event_argument.h"
@@ -104,6 +104,17 @@ const char kTestSmaps2[] =
     "MMUPageSize:           4 kB\n"
     "Locked:                0 kB\n"
     "VmFlags: rd wr mr mw me ac sd\n";
+
+void CreateAndSetSmapsFileForTesting(const char* smaps_string, ScopedFD& fd) {
+  FilePath temp_path;
+  FILE* temp_file = CreateAndOpenTemporaryFile(&temp_path);
+  fd.reset(fileno(temp_file));
+  ASSERT_TRUE(fd.is_valid());
+
+  ASSERT_TRUE(
+      base::WriteFileDescriptor(fd.get(), smaps_string, strlen(smaps_string)));
+}
+
 }  // namespace
 
 TEST(ProcessMemoryMapsDumpProviderTest, ParseProcSmaps) {
@@ -116,23 +127,24 @@ TEST(ProcessMemoryMapsDumpProviderTest, ParseProcSmaps) {
 
   // Emulate a non-existent /proc/self/smaps.
   ProcessMemoryDump pmd_invalid(nullptr /* session_state */);
-  std::ifstream non_existent_file("/tmp/does-not-exist");
-  ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &non_existent_file;
-  CHECK_EQ(false, non_existent_file.good());
+  ScopedFD non_existent_fd(open("/tmp/does-not-exist", O_RDONLY));
+  ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &non_existent_fd;
+  CHECK_EQ(false, non_existent_fd.is_valid());
   pmmdp->OnMemoryDump(dump_args, &pmd_invalid);
   ASSERT_FALSE(pmd_invalid.has_process_mmaps());
 
   // Emulate an empty /proc/self/smaps.
-  std::ifstream empty_file("/dev/null");
+  ScopedFD empty_file(open("/dev/null", O_RDONLY));
+  ASSERT_TRUE(empty_file.is_valid());
   ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &empty_file;
-  CHECK_EQ(true, empty_file.good());
   pmmdp->OnMemoryDump(dump_args, &pmd_invalid);
   ASSERT_FALSE(pmd_invalid.has_process_mmaps());
 
   // Parse the 1st smaps file.
   ProcessMemoryDump pmd_1(nullptr /* session_state */);
-  std::istringstream test_smaps_1(kTestSmaps1);
-  ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &test_smaps_1;
+  ScopedFD temp_fd1;
+  CreateAndSetSmapsFileForTesting(kTestSmaps1, temp_fd1);
+  ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &temp_fd1;
   pmmdp->OnMemoryDump(dump_args, &pmd_1);
   ASSERT_TRUE(pmd_1.has_process_mmaps());
   const auto& regions_1 = pmd_1.process_mmaps()->vm_regions();
@@ -162,8 +174,9 @@ TEST(ProcessMemoryMapsDumpProviderTest, ParseProcSmaps) {
 
   // Parse the 2nd smaps file.
   ProcessMemoryDump pmd_2(nullptr /* session_state */);
-  std::istringstream test_smaps_2(kTestSmaps2);
-  ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &test_smaps_2;
+  ScopedFD temp_fd2;
+  CreateAndSetSmapsFileForTesting(kTestSmaps2, temp_fd2);
+  ProcessMemoryMapsDumpProvider::proc_smaps_for_testing = &temp_fd2;
   pmmdp->OnMemoryDump(dump_args, &pmd_2);
   ASSERT_TRUE(pmd_2.has_process_mmaps());
   const auto& regions_2 = pmd_2.process_mmaps()->vm_regions();