Implement InterpolationMedium to filter animated images

Source/core/rendering/ImageQualityController.cpp

Index: Source/core/rendering/ImageQualityController.cpp
diff --git a/Source/core/rendering/ImageQualityController.cpp b/Source/core/rendering/ImageQualityController.cpp
index c9bdae70ea909590f357431089115d51c5025062..bd15ed251b6afe2c0e8adf1ec166d627bb8b4d10 100644
--- a/Source/core/rendering/ImageQualityController.cpp
+++ b/Source/core/rendering/ImageQualityController.cpp
@@ -60,6 +60,18 @@ void ImageQualityController::remove(RenderObject* renderer)
     }
 }
 
+InterpolationQuality ImageQualityController::chooseInterpolationQuality(GraphicsContext* context, RenderObject* object, Image* image, const void* layer, const LayoutSize& layoutSize)
+{
+    if (shouldPaintAtLowQuality(context, object, image, layer, layoutSize))
+        return InterpolationLow;

[Stephen White, 2014/03/18 17:26:43]

We actually might want to consider using Medium here as well, to get mips for
minification on animated HTML elements as well. But we can consider that in a
separate change.

[Alpha Left Google, 2014/03/18 22:59:13]

That's right. We can update that later.

+
+    // For images that are potentially animated we paint them at low quality.

[Stephen Chennney, 2014/03/18 12:56:32]

This comment doesn't seem to match the code. Is the problem the comment or the
semantics of InterpolationMedium.

[Alpha Left Google, 2014/03/18 22:59:13]

The code is correct. I've updated the comments.

+    if (image && image->maybeAnimated())
+        return InterpolationMedium;
+
+    return InterpolationDefault;
+}
+
 ImageQualityController::~ImageQualityController()
 {
     // This will catch users of ImageQualityController that forget to call cleanUp.
@@ -137,10 +149,6 @@ bool ImageQualityController::shouldPaintAtLowQuality(GraphicsContext* context, R
     if (object->style()->imageRendering() == ImageRenderingOptimizeContrast)
         return true;
 
-    // For images that are potentially animated we paint them at low quality.
-    if (image->maybeAnimated())
-        return true;
-
     // Look ourselves up in the hashtables.
     ObjectLayerSizeMap::iterator i = m_objectLayerSizeMap.find(object);
     LayerSizeMap* innerMap = i != m_objectLayerSizeMap.end() ? &i->value : 0;