Test scaling for small images

We don't want to test small images on Gold because they are
not interested to look at.  Instead, I wrote a unit test to
verify that scaling small images does not cause crashes.

BUG=skia:

Review URL: https://codereview.chromium.org/1287863004

1 files changed, 11 insertions, 0 deletions

diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index 3465c1df5b..ae9524b8b7 100644
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -55,6 +55,17 @@ public:
      *  scale that it can natively support
      */
     SkISize getScaledDimensions(float desiredScale) const {
+        // Negative and zero scales are errors.
+        SkASSERT(desiredScale > 0.0f);
+        if (desiredScale <= 0.0f) {
+            return SkISize::Make(0, 0);
+        }
+
+        // Upscaling is not supported. Return the original size if the client
+        // requests an upscale.
+        if (desiredScale >= 1.0f) {
+            return this->getInfo().dimensions();
+        }
         return this->onGetScaledDimensions(desiredScale);
     }