Use --gtest_flagfile for --gtest_filter in unit test launcher

base/test/launcher/unit_test_launcher.cc

 // Copyright 2013 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 "base/test/launcher/unit_test_launcher.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
@@ skipping 95 matching lines @@
       return false;
     *path = path->AppendASCII("test_results.xml");
     return true;
   }
 
   CommandLine GetCommandLineForChildGTestProcess(
       const std::vector<std::string>& test_names,
       const base::FilePath& output_file) override {
     CommandLine new_cmd_line(*CommandLine::ForCurrentProcess());
 
+    if (!temp_dir_.IsValid()) {

[sky, 2015/10/29 17:32:34]

nit: no {}. That said, I would likely move this into the CHECK, eg:

CHECK(temp_dir_.IsValid() || temp_dir_.CreateUniqueTempDir());

[Paweł Hajdan Jr., 2015/10/29 18:43:20]

Done.

+      CHECK(temp_dir_.CreateUniqueTempDir());
+    }
+    FilePath temp_file;
+    CHECK(CreateTemporaryFileInDir(temp_dir_.path(), &temp_file));
+    std::string long_flags(
+        std::string("--") + kGTestFilterFlag + "=" +
+        JoinString(test_names, ":"));
+    CHECK_EQ(static_cast<int>(long_flags.size()),
+             WriteFile(temp_file,
+                       long_flags.data(),
+                       static_cast<int>(long_flags.size())));
+
     new_cmd_line.AppendSwitchPath(switches::kTestLauncherOutput, output_file);
-    new_cmd_line.AppendSwitchASCII(kGTestFilterFlag,
-                                   JoinString(test_names, ":"));
+    new_cmd_line.AppendSwitchPath(kGTestFlagfileFlag, temp_file);
     new_cmd_line.AppendSwitch(kSingleProcessTestsFlag);
 
     return new_cmd_line;
   }
 
   std::string GetWrapperForChildGTestProcess() override {
     return std::string();
   }
 
   void RelaunchTests(TestLauncher* test_launcher,
                      const std::vector<std::string>& test_names,
                      int launch_flags) override {
     // Relaunch requested tests in parallel, but only use single
     // test per batch for more precise results (crashes, etc).
     for (const std::string& test_name : test_names) {
       std::vector<std::string> batch;
       batch.push_back(test_name);
       RunUnitTestsBatch(test_launcher, this, batch, launch_flags);
     }
   }
 
+  ScopedTempDir temp_dir_;
+
   DISALLOW_COPY_AND_ASSIGN(DefaultUnitTestPlatformDelegate);
 };
 
 bool GetSwitchValueAsInt(const std::string& switch_name, int* result) {
   if (!CommandLine::ForCurrentProcess()->HasSwitch(switch_name))
     return true;
 
   std::string switch_value =
       CommandLine::ForCurrentProcess()->GetSwitchValueASCII(switch_name);
   if (!StringToInt(switch_value, result) || *result < 1) {
@@ skipping 430 matching lines @@
     TestLauncher* test_launcher,
     const std::vector<std::string>& test_names) {
   ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE,
       Bind(&RunUnitTestsSerially, test_launcher, platform_delegate_, test_names,
            use_job_objects_ ? TestLauncher::USE_JOB_OBJECTS : 0));
   return test_names.size();
 }
 
 }  // namespace base