Fix build error on Windows stand alone build.

R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/299353008

pdfium.gyp

diff --git a/pdfium.gyp b/pdfium.gyp
index 1b0bae0..e8e706e 100644
--- a/pdfium.gyp
+++ b/pdfium.gyp
@@ -119,23 +119,27 @@
             'fpdfsdk/src/fpdfsdkdll.rc',
           ],
         }],
-        ['OS=="mac"', {
-          'link_settings': {
-            'libraries': [
-              '$(SDKROOT)/System/Library/Frameworks/AppKit.framework',
-              '$(SDKROOT)/System/Library/Frameworks/CoreFoundation.framework',
+      ],
+      'all_dependent_settings': {
+        'msvs_settings': {
+          'VCLinkerTool': {
+            'AdditionalDependencies': [
+              'advapi32.lib',
+              'gdi32.lib',
+              'user32.lib',
             ],
           },
-        }],
-      ],
-      'msvs_settings': {
-        'VCLinkerTool': {
-          'AdditionalDependencies': [
-            'advapi32.lib',
-            'gdi32.lib',
-            'user32.lib',
-          ],
         },
+        'conditions': [
+          ['OS=="mac"', {
+            'link_settings': {
+              'libraries': [
+                '$(SDKROOT)/System/Library/Frameworks/AppKit.framework',
+                '$(SDKROOT)/System/Library/Frameworks/CoreFoundation.framework',
+              ],
+            },
+          }],
+        ],
       },
     },
     {