respect srgb gamma when building mips

src/core/SkPixmap.cpp

Index: src/core/SkPixmap.cpp
diff --git a/src/core/SkPixmap.cpp b/src/core/SkPixmap.cpp
index bd551ed9d3dd09a2a2c51ddc05cbbdb31c4b9b1f..8756ab3f56b8c9d8af52c33448e300823bae1d2d 100644
--- a/src/core/SkPixmap.cpp
+++ b/src/core/SkPixmap.cpp
@@ -52,6 +52,10 @@ bool SkPixmap::reset(const SkMask& src) {
     return false;
 }
 
+void SkPixmap::setColorSpace(sk_sp<SkColorSpace> cs) {
+    fInfo = fInfo.makeColorSpace(cs);
+}
+
 bool SkPixmap::extractSubset(SkPixmap* result, const SkIRect& subset) const {
     SkIRect srcRect, r;
     srcRect.set(0, 0, this->width(), this->height());