bail out of ChooseBitmapXferProc with a color space

This fixes the paint-color parts of the gamut GM,
and a handful of other similar problems.

We'll still memset in the blitter, just after we get in the right gamut.

BUG=skia:6679

Change-Id: I2b16259ad689c63ae304fb600802acf9125b8c25
Reviewed-on: https://skia-review.googlesource.com/17922
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

src/core/SkDraw.cpp

@@ -98,7 +98,7 @@ static BitmapXferProc ChooseBitmapXferProc(const SkPixmap& dst, const SkPaint& p
                                            uint32_t* data) {
     // todo: we can apply colorfilter up front if no shader, so we wouldn't
     // need to abort this fastpath
-    if (paint.getShader() || paint.getColorFilter()) {
+    if (paint.getShader() || paint.getColorFilter() || dst.colorSpace()) {
         return nullptr;
     }