Switched to JDCT_ISLOW for Android.

Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp

Index: Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
diff --git a/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp b/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
index 5da5d357157ecd6047d9358012230ff7a20178f6..725f2fe98ffe24c9ada571d68cbc0c114c488b49 100644
--- a/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
+++ b/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
@@ -75,13 +75,14 @@ inline bool colorSpaceHasAlpha(J_COLOR_SPACE) { return false; }
 #endif
 
 #if USE(LOW_QUALITY_IMAGE_NO_JPEG_DITHERING)
-inline J_DCT_METHOD dctMethod() { return JDCT_IFAST; }
 inline J_DITHER_MODE ditherMode() { return JDITHER_NONE; }
 #else
-inline J_DCT_METHOD dctMethod() { return JDCT_ISLOW; }
 inline J_DITHER_MODE ditherMode() { return JDITHER_FS; }
 #endif
 
+// We always use JDCT_ISLOW, since JDCT_IFAST can introduce artifacts.
+inline J_DCT_METHOD dctMethod() { return JDCT_ISLOW; }
+
 #if USE(LOW_QUALITY_IMAGE_NO_JPEG_FANCY_UPSAMPLING)
 inline bool doFancyUpsampling() { return false; }
 #else