Pass a context pointer to Framebuffer[Impl]::getSamplePosition

BUG=angleproject:2464

Change-Id: Icd260db9bbd11699b2d0f6152e898c38baa4844d
Reviewed-on: https://chromium-review.googlesource.com/1052219
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>
diff --git a/src/libANGLE/renderer/null/FramebufferNULL.cpp b/src/libANGLE/renderer/null/FramebufferNULL.cpp
index 30dba62..ed60218 100644
--- a/src/libANGLE/renderer/null/FramebufferNULL.cpp
+++ b/src/libANGLE/renderer/null/FramebufferNULL.cpp
@@ -191,7 +191,9 @@
     return gl::NoError();
 }
 
-gl::Error FramebufferNULL::getSamplePosition(size_t index, GLfloat *xy) const
+gl::Error FramebufferNULL::getSamplePosition(const gl::Context *context,
+                                             size_t index,
+                                             GLfloat *xy) const
 {
     return gl::NoError();
 }