Various minor cross-platform changes

src/gpu/gl/GrGLGpu.cpp

Index: src/gpu/gl/GrGLGpu.cpp
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index 1a2896350e3077c9324a4b8e284f87136d6f3439..44b75059da737dc83eabb693f892257fc1ee2d70 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -564,10 +564,6 @@ bool GrGLGpu::onWritePixels(GrSurface* surface,
                             int left, int top, int width, int height,
                             GrPixelConfig config, const void* buffer,
                             size_t rowBytes) {
-    if (nullptr == buffer) {
-        return false;
-    }
-
     GrGLTexture* glTex = static_cast<GrGLTexture*>(surface->asTexture());
     if (!glTex) {
         return false;