Mac cloud print proxy work.

printing/printing.gyp

Index: printing/printing.gyp
diff --git a/printing/printing.gyp b/printing/printing.gyp
index ac87ab36d9b713d8a3ec1b2d9e2d4c6e5a3c876d..7acb6d738ad8c72aaac30f8380feabb6d9e87562 100644
--- a/printing/printing.gyp
+++ b/printing/printing.gyp
@@ -112,12 +112,6 @@
           ],
         }],
         ['use_cups==1', {
-          'link_settings': {
-            'libraries': [
-              '-lcups',
-              '-lgcrypt',
-            ],
-          },
           'defines': [
             # PRINT_BACKEND_AVAILABLE disables the default dummy implementation
             # of the print backend and enables a custom implementation instead.
@@ -128,6 +122,22 @@
             'backend/cups_helper.h',
             'backend/print_backend_cups.cc',
           ],
+          'conditions': [
+            ['OS=="mac"', {
+              'link_settings': {
+                'libraries': [
+                  '$(SDKROOT)/usr/lib/libcups.dylib',
+                ]
+              },
+            }, {
+              'link_settings': {
+                'libraries': [
+                  '-lcups',
+                  '-lgcrypt',
+                ],
+              },
+            }],              
+          ],
         }],
       ],
     },