Clarify onCreateScalerContext failure modes.

This should not change any behavior, but addresses some readability
concerns.

Change-Id: I2614beaed7b5722a3af2c49ab8f4ac16b56aa3a7
Reviewed-on: https://skia-review.googlesource.com/4393
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/src/ports/SkFontHost_FreeType.cpp b/src/ports/SkFontHost_FreeType.cpp
index 8b233ff..2eaf2bf 100644
--- a/src/ports/SkFontHost_FreeType.cpp
+++ b/src/ports/SkFontHost_FreeType.cpp
@@ -618,7 +618,7 @@
     auto c = skstd::make_unique<SkScalerContext_FreeType>(
             sk_ref_sp(const_cast<SkTypeface_FreeType*>(this)), effects, desc);
     if (!c->success()) {
-        c = nullptr;
+        return nullptr;
     }
     return c.release();
 }