Remove all code related to NaCl

BUG=skia:3600
DOCS_PREVIEW= https://skia.org/?cl=1036283002

Review URL: https://codereview.chromium.org/1036283002
diff --git a/gyp/gpu.gyp b/gyp/gpu.gyp
index 8e4cb07..7d3dad5 100644
--- a/gyp/gpu.gyp
+++ b/gyp/gpu.gyp
@@ -26,11 +26,7 @@
         'sources/': [ ['exclude', '_android.(h|cpp)$'],
         ],
       }],
-      ['skia_os != "nacl"', {
-        'sources/': [ ['exclude', '_nacl.(h|cpp)$'],
-        ],
-      }],
-      ['skia_os == "nacl" or skia_egl == 0', {
+      ['skia_egl == 0', {
         'sources/': [ ['exclude', '_egl.(h|cpp)$'],
         ],
       }],
@@ -170,13 +166,6 @@
             ],
           },
         }],
-        [ 'skia_os == "nacl"', {
-          'link_settings': {
-            'libraries': [
-              '-lppapi_gles2',
-            ],
-          },
-        }],
         [ 'skia_egl == 1', {
           'defines': [
             'SK_EGL=1',