Don't use a low-quality filter when painting images while others are animating.

third_party/WebKit/Source/core/layout/ImageQualityControllerTest.cpp

Index: third_party/WebKit/Source/core/layout/ImageQualityControllerTest.cpp
diff --git a/third_party/WebKit/Source/core/layout/ImageQualityControllerTest.cpp b/third_party/WebKit/Source/core/layout/ImageQualityControllerTest.cpp
index cefe8ee758deabd9ca1bab26ffefbc611b4082af..6a8b62f95ca0a1e3bb8a700f1645ff50c94397c8 100644
--- a/third_party/WebKit/Source/core/layout/ImageQualityControllerTest.cpp
+++ b/third_party/WebKit/Source/core/layout/ImageQualityControllerTest.cpp
@@ -177,6 +177,36 @@ TEST_F(ImageQualityControllerTest, LowQualityFilterForResizingImage)
     EXPECT_EQ(InterpolationMedium, controller()->chooseInterpolationQuality(*img, testImage.get(), testImage.get(), LayoutSize(4, 4)));
 }
 
+TEST_F(ImageQualityControllerTest, MediumQualityFilterForNotAnimatedWhileAnotherAnimates)
+{
+    MockTimer* mockTimer = new MockTimer(controller(), &ImageQualityController::highQualityRepaintTimerFired);
+    controller()->setTimer(mockTimer);
+    setBodyInnerHTML("<img id='myAnimatingImage' src='myimage'></img> <img id='myNonAnimatingImage' src='myimage2'></img>");
+    LayoutImage* animatingImage = toLayoutImage(document().getElementById("myAnimatingImage")->layoutObject());
+    LayoutImage* nonAnimatingImage = toLayoutImage(document().getElementById("myNonAnimatingImage")->layoutObject());
+
+    RefPtr<TestImageLowQuality> testImage = adoptRef(new TestImageLowQuality);
+    OwnPtr<PaintController> paintController = PaintController::create();
+    GraphicsContext context(*paintController);
+
+    // Paint once. This will kick off a timer to see if we resize it during that timer's execution.
+    EXPECT_EQ(InterpolationMedium, controller()->chooseInterpolationQuality(*animatingImage, testImage.get(), testImage.get(), LayoutSize(2, 2)));
+
+    // Go into low-quality mode now that the size changed.
+    EXPECT_EQ(InterpolationLow, controller()->chooseInterpolationQuality(*animatingImage, testImage.get(), testImage.get(), LayoutSize(3, 3)));
+
+    // The non-animating image receives a medium-quality filter, even though the other one is animating.
+    EXPECT_EQ(InterpolationMedium, controller()->chooseInterpolationQuality(*nonAnimatingImage, testImage.get(), testImage.get(), LayoutSize(4, 4)));
+
+    // Now the second image has animated, so it also gets painted with a low-quality filter.
+    EXPECT_EQ(InterpolationLow, controller()->chooseInterpolationQuality(*nonAnimatingImage, testImage.get(), testImage.get(), LayoutSize(3, 3)));
+
+    mockTimer->fire();
+    // The timer fired before painting at another size, so this doesn't count as animation. Therefore not painting at low quality for any image.
+    EXPECT_EQ(InterpolationMedium, controller()->chooseInterpolationQuality(*animatingImage, testImage.get(), testImage.get(), LayoutSize(4, 4)));
+    EXPECT_EQ(InterpolationMedium, controller()->chooseInterpolationQuality(*nonAnimatingImage, testImage.get(), testImage.get(), LayoutSize(4, 4)));
+}
+
 TEST_F(ImageQualityControllerTest, DontKickTheAnimationTimerWhenPaintingAtTheSameSize)
 {
     MockTimer* mockTimer = new MockTimer(controller(), &ImageQualityController::highQualityRepaintTimerFired);