Backed out changeset 6c8bf287d25b (bug 1462431) for web platform reftest failure. r=aosmond

image/RasterImage.cpp

@@ -340,7 +340,8 @@ RasterImage::LookupFrame(const IntSize& aSize,
     aFlags &= ~FLAG_DECODE_NO_PREMULTIPLY_ALPHA;
   }
 
-  IntSize requestedSize = GetDownscaleDecodeSize(aSize, aFlags);
+  IntSize requestedSize = CanDownscaleDuringDecode(aSize, aFlags)
+                        ? aSize : mSize;
   if (requestedSize.IsEmpty()) {
     // Can't decode to a surface of zero size.
     return LookupResult(MatchType::NOT_FOUND);
@@ -637,7 +638,11 @@ RasterImage::GetImageContainerSize(LayerManager* aManager,
     return IntSize(0, 0);
   }
 
-  return GetDownscaleDecodeSize(aSize, aFlags);
+  if (!CanDownscaleDuringDecode(aSize, aFlags)) {
+    return mSize;
+  }
+
+  return aSize;
 }
 
 NS_IMETHODIMP_(bool)
@@ -1367,46 +1372,39 @@ HaveSkia()
 #endif
 }
 
-IntSize
-RasterImage::GetDownscaleDecodeSize(const IntSize& aSize, uint32_t aFlags)
+bool
+RasterImage::CanDownscaleDuringDecode(const IntSize& aSize, uint32_t aFlags)
 {
   // Check basic requirements: downscale-during-decode is enabled, Skia is
   // available, this image isn't transient, we have all the source data and know
   // our size, and the flags allow us to do it.
-  if (!mHasSize || mTransient || !HaveSkia() || aSize == mSize ||
+  if (!mHasSize || mTransient || !HaveSkia() ||
       !gfxPrefs::ImageDownscaleDuringDecodeEnabled() ||
       !(aFlags & imgIContainer::FLAG_HIGH_QUALITY_SCALING)) {
-    return mSize;
+    return false;
   }
 
   // We don't downscale animated images during decode.
   if (mAnimationState) {
-    return mSize;
+    return false;
+  }
+
+  // Never upscale.
+  if (aSize.width >= mSize.width || aSize.height >= mSize.height) {
+    return false;
   }
 
   // Zero or negative width or height is unacceptable.
   if (aSize.width < 1 || aSize.height < 1) {
-    return mSize;
-  }
-
-  // We never upscale, but we may partially downscale nearer to the desired
-  // size if only one of the dimensions exceeds the native size.
-  IntSize decodeSize(aSize);
-  if (aSize.width > mSize.width) {
-    if (aSize.height > mSize.height) {
-      return mSize;
-    }
-    decodeSize.width = mSize.width;
-  } else if (aSize.height > mSize.height) {
-    decodeSize.height = mSize.height;
+    return false;
   }
 
   // There's no point in scaling if we can't store the result.
-  if (!SurfaceCache::CanHold(decodeSize)) {
-    return mSize;
+  if (!SurfaceCache::CanHold(aSize)) {
+    return false;
   }
 
-  return decodeSize;
+  return true;
 }
 
 ImgDrawResult
@@ -1436,8 +1434,7 @@ RasterImage::DrawInternal(DrawableSurface&& aSurface,
     aContext->Multiply(gfxMatrix::Scaling(scale.width, scale.height));
     region.Scale(1.0 / scale.width, 1.0 / scale.height);
 
-    couldRedecodeForBetterFrame =
-      GetDownscaleDecodeSize(aSize, aFlags) != mSize;
+    couldRedecodeForBetterFrame = CanDownscaleDuringDecode(aSize, aFlags);
   }
 
   if (!aSurface->Draw(aContext, region, aSamplingFilter, aFlags, aOpacity)) {
@@ -1862,12 +1859,15 @@ RasterImage::OptimalImageSizeForDest(const gfxSize& aDest, uint32_t aWhichFrame,
     return IntSize(0, 0);
   }
 
-  if (aSamplingFilter != SamplingFilter::GOOD) {
-    return mSize;
+  IntSize destSize = IntSize::Ceil(aDest.width, aDest.height);
+
+  if (aSamplingFilter == SamplingFilter::GOOD &&
+      CanDownscaleDuringDecode(destSize, aFlags)) {
+    return destSize;
   }
 
-  IntSize destSize = IntSize::Ceil(aDest.width, aDest.height);
-  return GetDownscaleDecodeSize(destSize, aFlags);
+  // We can't scale to this size. Use our intrinsic size for now.
+  return mSize;
 }
 
 } // namespace image

image/RasterImage.h

@@ -435,9 +435,9 @@ private: // data
   // Scaling.
   //////////////////////////////////////////////////////////////////////////////
 
-  // Determines the decode size depending on whether we can downscale during
-  // decode with the given parameters.
-  gfx::IntSize GetDownscaleDecodeSize(const nsIntSize& aSize, uint32_t aFlags);
+  // Determines whether we can downscale during decode with the given
+  // parameters.
+  bool CanDownscaleDuringDecode(const nsIntSize& aSize, uint32_t aFlags);
 
 
   // Error handling.

image/test/unit/test_imgtools.js

@@ -545,7 +545,7 @@ encodedBytes = streamToArray(istream);
 refName = "image2jpg32x16scaled.jpg";
 refFile = do_get_file(refName);
 istream = getFileInputStream(refFile);
-Assert.equal(istream.available(), 1222);
+Assert.equal(istream.available(), 1227);
 referenceBytes = streamToArray(istream);
 
 // compare the encoder's output to the reference file.