Get Mac viewer working with SDL

gyp/viewer.gyp

Index: gyp/viewer.gyp
diff --git a/gyp/viewer.gyp b/gyp/viewer.gyp
index b2563ef5371d776ff478b7e45e8d2d5b3d7325ad..11d093c15bedede936f1f66fa30c92d85b60e6c7 100644
--- a/gyp/viewer.gyp
+++ b/gyp/viewer.gyp
@@ -32,6 +32,7 @@
       'sources': [
         '../gm/gm.cpp',
         '<!@(python find.py ../tools/viewer "*.cpp")',
+        '<!@(python find.py ../tools/viewer "*.h")',
 
         # views (subset of files for the Android build)
         '../src/views/SkEvent.cpp',
@@ -85,6 +86,11 @@
             ],
           },
         }],
+        [ 'skia_os == "mac"', {
+          'dependencies': [
+            'sdl.gyp:sdl',
+          ],
+        }],
         ['skia_os != "android"', {
           'sources/': [
             ['exclude', '_android.(h|cpp)$'],