Enable warnings-as-errors on Windows.
Review URL: https://codereview.appspot.com/7066054

git-svn-id: http://skia.googlecode.com/svn/trunk@7094 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/common_conditions.gypi b/gyp/common_conditions.gypi
index a14be76..e28985f 100644
--- a/gyp/common_conditions.gypi
+++ b/gyp/common_conditions.gypi
@@ -30,7 +30,7 @@
         'msvs_settings': {
           'VCCLCompilerTool': {
             'WarningLevel': '1',
-            'WarnAsError': 'false',
+            'WarnAsError': 'true',
             'DebugInformationFormat': '3',
             'AdditionalOptions': [ '/MP' ],
           },