Revert of clang/win: Stop passing -Qunused-arguments.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index d7fa5d6308317fdd78af3446dd381e1e50dbae3e..ee31a8d28ba7fec7d927613fae4a61577e706d4e 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -5630,19 +5630,10 @@
                     'Optimization': '2',
                     # 1, favorSpeed - Favor fast code (/Ot)
                     'FavorSizeOrSpeed': '1',
+                    # This implies link time code generation.
+                    'WholeProgramOptimization': 'true',
                   },
                 },
-                # TODO(thakis): Remove clang==0 here, https://crbug.com/598772
-                'conditions': [
-                  ['clang==0', {
-                    'msvs_settings': {
-                      'VCCLCompilerTool': {
-                        # This implies link time code generation.
-                        'WholeProgramOptimization': 'true',
-                      },
-                    },
-                  }],
-                ],
               }],
             ],
           }],
@@ -5750,6 +5741,7 @@
           'VCCLCompilerTool': {
             'AdditionalOptions': ['/MP'],
             'MinimalRebuild': 'false',
+            'BufferSecurityCheck': 'true',
             'EnableFunctionLevelLinking': 'true',
             'RuntimeTypeInfo': 'false',
             'WarningLevel': '4',
@@ -5822,14 +5814,6 @@
             }],
           ],
           'conditions': [
-            ['clang==0', {
-              'VCCLCompilerTool': {
-                 # TODO(thakis): Enable this with clang too,
-                 # https://crbug.com/598767
-                 'BufferSecurityCheck': 'true',
-              },
-            }],
-
             # Building with Clang on Windows is a work in progress and very
             # experimental. See crbug.com/82385.
             # Keep this in sync with the similar blocks in build/config/compiler/BUILD.gn
@@ -5848,6 +5832,7 @@
                   '/FIIntrin.h',
 
                   # TODO(hans): Make this list shorter eventually, http://crbug.com/504657
+                  '-Qunused-arguments',  # http://crbug.com/504658
                   '-Wno-microsoft-enum-value',  # http://crbug.com/505296
                   '-Wno-unknown-pragmas',  # http://crbug.com/505314
                   '-Wno-microsoft-cast',  # http://crbug.com/550065