Update from https://crrev.com/314320

base/test/launcher/test_launcher_ios.cc

Index: base/test/launcher/test_launcher_ios.cc
diff --git a/base/test/launcher/test_launcher_ios.cc b/base/test/launcher/test_launcher_ios.cc
index 7028133b5247a27900658b409219219404ae2605..ecd31aedf5d00cb3754b0c1d4220b65e1dce3e51 100644
--- a/base/test/launcher/test_launcher_ios.cc
+++ b/base/test/launcher/test_launcher_ios.cc
@@ -129,6 +129,14 @@ class IOSUnitTestPlatformDelegate : public base::UnitTestPlatformDelegate {
     return dir_exe_.AppendASCII("iossim").value();
   }
 
+  void RelaunchTests(base::TestLauncher* test_launcher,
+                     const std::vector<std::string>& test_names,
+                     int launch_flags) override {
+    // Relaunch all tests in one big batch, since overhead of smaller batches
+    // is too big for serialized runs inside ios simulator.
+    RunUnitTestsBatch(test_launcher, this, test_names, launch_flags);
+  }
+
  private:
   // Directory containing test launcher's executable.
   base::FilePath dir_exe_;