Attempt to improve lifetime management of SkGlyphCache in Ganesh atlas text code.

src/core/SkGlyphCache.h

Index: src/core/SkGlyphCache.h
diff --git a/src/core/SkGlyphCache.h b/src/core/SkGlyphCache.h
index fd3ef66028aba7500dc3c84cf1582d813d7eaecd..2a96370045f8378b93f5ac4de318732677be2c72 100644
--- a/src/core/SkGlyphCache.h
+++ b/src/core/SkGlyphCache.h
@@ -277,7 +277,7 @@ class SkAutoGlyphCache : public std::unique_ptr<SkGlyphCache, SkGlyphCache::Atta
 public:
     /** deprecated: use get() */
     SkGlyphCache* getCache() const { return this->get(); }
-
+    SkAutoGlyphCache() = default;
     SkAutoGlyphCache(SkGlyphCache* cache) : INHERITED(cache) {}
     SkAutoGlyphCache(SkTypeface* typeface, const SkScalerContextEffects& effects,
                      const SkDescriptor* desc)