Format GN files and add a presubmit check that GN is properly formatted

build/config/compiler/BUILD.gn

 # Copyright (c) 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.
 
 import("//build/config/android/config.gni")
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 if (current_cpu == "mipsel" || current_cpu == "mips64el") {
   import("//build/config/mips.gni")
@@ skipping 60 matching lines @@
       # //build/config/gcc:symbol_visibility_hidden.
       "-fvisibility-inlines-hidden",
 
       # We need the frame pointer for CPU and heap profiling.
       "-fno-omit-frame-pointer",
     ]
     cflags_cc += common_flags
     cflags_objcc += common_flags
 
     # Linker warnings.
-    if ((current_cpu != "arm") && !is_mac) {
+    if (current_cpu != "arm" && !is_mac) {
       # TODO(jochen): Enable this on chromeos on arm. http://crbug.com/356580
       ldflags += [ "-Wl,--fatal-warnings" ]
     }
 
     # Common options for AddressSanitizer, LeakSanitizer, ThreadSanitizer and
     # MemorySanitizer
     if (using_sanitizer) {
-      cflags += [
-        "-gline-tables-only",
-      ]
+      cflags += [ "-gline-tables-only" ]
     }
     if (is_asan) {
       cflags += [ "-fsanitize=address" ]
       ldflags += [ "-fsanitize=address" ]
     }
     if (is_lsan) {
       cflags += [ "-fsanitize=leak" ]
       ldflags += [ "-fsanitize=leak" ]
     }
     if (is_tsan) {
@@ skipping 90 matching lines @@
           # Else building libyuv gives clang's register allocator issues,
           # see llvm.org/PR15798 / crbug.com/233709
           "-mno-omit-leaf-frame-pointer",
 
           # Align the stack on 16-byte boundaries, http://crbug.com/418554.
           "-mstack-alignment=16",
           "-mstackrealign",
         ]
       }
     } else if (current_cpu == "arm") {
-
       cflags += [
         "-march=$arm_arch",
         "-mfloat-abi=$arm_float_abi",
       ]
       if (arm_tune != "") {
         cflags += [ "-mtune=$arm_tune" ]
       }
       if (arm_use_thumb) {
         cflags += [ "-mthumb" ]
         if (is_android && !is_clang) {  # Clang doesn't support this option.
@@ skipping 14 matching lines @@
           # size and performance in gcc 4.9.
           "-fno-caller-saves",
         ]
       }
     } else if (current_cpu == "mipsel") {
       # We have to explicitly request exceptions to get good heap profiles from
       # tcmalloc.
       if (is_debug || is_release) {
         cflags += [
           "-fexceptions",
-          "-funwind-tables"
+          "-funwind-tables",
         ]
       }
 
       if (mips_arch_variant == "r6") {
         cflags += [
           "-mips32r6",
           "-Wa,-mips32r6",
         ]
         if (is_android) {
           ldflags += [
@@ skipping 40 matching lines @@
     }
 
     if (current_cpu != "mipsel") {
       cflags += [ "-fno-exceptions" ]
     }
   }
 
   # Linux/Android common flags setup.
   # ---------------------------------
   if (is_linux || is_android) {
-    cflags += [
-      "-fPIC",
-    ]
+    cflags += [ "-fPIC" ]
 
     ldflags += [
       "-fPIC",
       "-Wl,-z,noexecstack",
       "-Wl,-z,now",
       "-Wl,-z,relro",
     ]
   }
 
   # Linux-specific compiler flags setup.
@@ skipping 193 matching lines @@
 default_warning_flags = []
 default_warning_flags_cc = []
 if (is_win) {
   if (current_cpu != "x86") {
     default_warning_flags += [ "/WX" ]  # Treat warnings as errors.
   }
 
   default_warning_flags += [
     # Permanent.
     "/wd4091",  # typedef warning from dbghelp.h
+
     # Investigate.
     "/wd4312",  # int to pointer of greater size conversion.
     "/wd4838",  # Narrowing conversion required.
     "/wd4172",  # Returning address of local.
     "/wd4005",  # Redefinition of macros for PRId64 etc.
     "/wd4311",  # Pointer truncation from PVOID to DWORD.
     "/wd4477",  # Format string requires wchar_t*
   ]
 } else {
   # Common GCC warning setup.
@@ skipping 243 matching lines @@
       cflags = [ "/Zi" ]  # Produce PDB file, no edit and continue.
     }
     ldflags = [ "/DEBUG" ]
   } else {
     cflags = [
       "-g3",
       "-ggdb3",
     ]
   }
 }