respect srgb gamma when building mips

src/gpu/SkGr.cpp

Index: src/gpu/SkGr.cpp
diff --git a/src/gpu/SkGr.cpp b/src/gpu/SkGr.cpp
index 2127c367444cf86e7e58584556187d6e4368a3d9..4906cbbdcfc5bcbce1d2a0d2adfe9102dcb4780f 100644
--- a/src/gpu/SkGr.cpp
+++ b/src/gpu/SkGr.cpp
@@ -344,10 +344,9 @@ GrTexture* GrGenerateMipMapsAndUploadToTexture(GrContext* ctx, const SkBitmap& b
         return texture.release();
     }
 
-    // SkMipMap::Build doesn't handle sRGB data correctly (yet).
-    // Failover to the GL code-path for now.
-    if (kLinear_SkColorProfileType != bitmap.profileType()) {
-        return nullptr;
+    SkMipMap::SrcGammaMode mode = SkMipMap::kRespect_SrcGammaMode;
+    if (/* we're in compatibility-mode-for-L32*/true) {
+        mode = SkMipMap::kIgnore_SrcGammaMode;
     }
 
     SkASSERT(sizeof(int) <= sizeof(uint32_t));
@@ -365,7 +364,7 @@ GrTexture* GrGenerateMipMapsAndUploadToTexture(GrContext* ctx, const SkBitmap& b
         sk_throw();
     }
 
-    SkAutoTDelete<SkMipMap> mipmaps(SkMipMap::Build(pixmap, nullptr));
+    SkAutoTDelete<SkMipMap> mipmaps(SkMipMap::Build(pixmap, mode, nullptr));
     if (!mipmaps) {
         return nullptr;
     }