Improve NaCl support

- Add nacl_make script to build Skia targets for NaCl using gyp
- Add nacl_interface for command-line apps
- Add nacl_sample as front-end for SampleApp
- Add freetype to DEPS
- Various gyp tweaks for NaCl

TODO:
- Implement GL interface
- Implement font host
- Fix plumbing so that SampleApp works properly
Review URL: https://codereview.appspot.com/6671044

git-svn-id: http://skia.googlecode.com/svn/trunk@6245 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/gpu.gyp b/gyp/gpu.gyp
index 9cb0698..d5223e4 100644
--- a/gyp/gpu.gyp
+++ b/gyp/gpu.gyp
@@ -21,6 +21,10 @@
         'sources/': [ ['exclude', '_android.(h|cpp)$'],
         ],
       }],
+      ['skia_os != "nacl"', {
+        'sources/': [ ['exclude', '_nacl.(h|cpp)$'],
+        ],
+      }],
       [ 'skia_os == "android"', {
         'defines': [
           'GR_ANDROID_BUILD=1',
@@ -209,10 +213,18 @@
           'link_settings': {
             'libraries': [
               '-lGL',
+              '-lGLU',
               '-lX11',
             ],
           },
         }],
+        [ 'skia_os == "nacl"', {
+          'link_settings': {
+            'libraries': [
+              '-lppapi_gles2',
+            ],
+          },
+        }],
         [ 'skia_mesa and skia_os == "linux"', {
           'link_settings': {
             'libraries': [