Enable 'treating warnings as errors' for 64 bit Win builds

build_gyp/standalone.gypi

Index: build_gyp/standalone.gypi
diff --git a/build_gyp/standalone.gypi b/build_gyp/standalone.gypi
index 67ed204409e7c0c08d77c66f38157eb6c6de41d8..be18b5006c905361938211452b179dc33c6bd17c 100644
--- a/build_gyp/standalone.gypi
+++ b/build_gyp/standalone.gypi
@@ -300,6 +300,7 @@
         'EnableFunctionLevelLinking': 'true',
         'RuntimeTypeInfo': 'false',
         'WarningLevel': '3',
+        'WarnAsError': 'true',
         'DebugInformationFormat': '3',
         'Detect64BitPortabilityProblems': 'false',
         'conditions': [
@@ -311,13 +312,6 @@
           }, {
             'ExceptionHandling': '0',
           }],
-          ['target_arch=="x64"', {
-            # 64-bit warnings need to be resolved.
-            # https://code.google.com/p/pdfium/issues/detail?id=101
-            'WarnAsError': 'false',
-          }, {
-            'WarnAsError': 'true',
-          }],
           ['clang==1', {
             'AdditionalOptions': [
               # Don't warn about unused function parameters.