Enable "unreachable code" warning for MSVC.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index c5a8f40f105353f4f14ec8c6546f0f88c37fbb30..340df94b26229140d0b597ae5e011dd78dc43457 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -4916,6 +4916,11 @@
                 },
               },
             },
+            # Warning 4702 should be re-enabled once Express users are updated
+            # to VS2013 Update 2.

[scottmg, 2014/05/22 23:39:06]

Please add crbug/what 4702 is here.

[Peter Kasting, 2014/05/23 17:51:16]

Done.

+            'msvs_disabled_warnings': [
+              4702
+            ],
             'msvs_settings': {
               'VCLinkerTool': {
                 # Explicitly required when using the ATL with express
@@ -4943,12 +4948,12 @@
           '$(VSInstallDir)/VC/atlmfc/include',
         ],
         'msvs_cygwin_shell': 0,
-        'msvs_disabled_warnings': [4351, 4355, 4396, 4503, 4819,
+        'msvs_disabled_warnings': [
+          4351, 4355, 4396, 4503, 4819,
           # TODO(maruel): These warnings are level 4. They will be slowly
           # removed as code is fixed.
           4100, 4121, 4125, 4127, 4130, 4131, 4189, 4201, 4238, 4244, 4245,
-          4310, 4428, 4481, 4505, 4510, 4512, 4530, 4610, 4611, 4701, 4702,
-          4706,
+          4310, 4428, 4481, 4505, 4510, 4512, 4530, 4610, 4611, 4701, 4706,
         ],
         'msvs_settings': {
           'VCCLCompilerTool': {