Add SkNativeGLContext implementation for iOS.

R=caryclark@google.com
Review URL: https://codereview.appspot.com/6589055

git-svn-id: http://skia.googlecode.com/svn/trunk@5767 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/gpu/gl/SkNativeGLContext.h b/include/gpu/gl/SkNativeGLContext.h
index 36461ba..52118da 100644
--- a/include/gpu/gl/SkNativeGLContext.h
+++ b/include/gpu/gl/SkNativeGLContext.h
@@ -12,7 +12,6 @@
 
 #if defined(SK_BUILD_FOR_MAC)
     #include <AGL/agl.h>
-
 #elif defined(SK_BUILD_FOR_ANDROID)
     #include <GLES2/gl2.h>
     #include <EGL/egl.h>
@@ -51,6 +50,8 @@
         EGLContext fOldEGLContext;
         EGLDisplay fOldDisplay;
         EGLSurface fOldSurface;
+    #elif defined(SK_BUILD_FOR_IOS)
+        void* fEAGLContext;
     #endif
     };
 
@@ -75,6 +76,8 @@
     EGLContext fContext;
     EGLDisplay fDisplay;
     EGLSurface fSurface;
+#elif defined(SK_BUILD_FOR_IOS)
+    void* fEAGLContext;
 #endif
 };