Mojo: clang-format mojo/public/c/... and add a presubmit check.

mojo/public/c/system/tests/macros_unittest.cc

 // Copyright 2014 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.
 
 // This file tests the C Mojo system macros and consists of "positive" tests,
 // i.e., those verifying that things work (without compile errors, or even
 // warnings if warnings are treated as errors).
 // TODO(vtl): Fix no-compile tests (which are all disabled; crbug.com/105388)
 // and write some "negative" tests.
 
@@ skipping 40 matching lines @@
   EXPECT_EQ(4u, MOJO_ALIGNOF(int32_t));
   EXPECT_EQ(8u, MOJO_ALIGNOF(int64_t));
   EXPECT_EQ(8u, MOJO_ALIGNOF(double));
 }
 
 // These structs are used in the Alignas test. Define them globally to avoid
 // MSVS warnings/errors.
 #if defined(_MSC_VER)
 #pragma warning(push)
 // Disable the warning "structure was padded due to __declspec(align())".
-#pragma warning(disable:4324)
+#pragma warning(disable : 4324)
 #endif
-struct MOJO_ALIGNAS(1) StructAlignas1 { char x; };
-struct MOJO_ALIGNAS(4) StructAlignas4 { char x; };
-struct MOJO_ALIGNAS(8) StructAlignas8 { char x; };
+struct MOJO_ALIGNAS(1) StructAlignas1 {
+  char x;
+};
+struct MOJO_ALIGNAS(4) StructAlignas4 {
+  char x;
+};
+struct MOJO_ALIGNAS(8) StructAlignas8 {
+  char x;
+};
 #if defined(_MSC_VER)
 #pragma warning(pop)
 #endif
 
 TEST(MacrosTest, Alignas) {
   EXPECT_EQ(1u, MOJO_ALIGNOF(StructAlignas1));
   EXPECT_EQ(4u, MOJO_ALIGNOF(StructAlignas4));
   EXPECT_EQ(8u, MOJO_ALIGNOF(StructAlignas8));
 }
 
 }  // namespace
 }  // namespace mojo