Tweak libpng encoding parameters to increase speed on very large images.

ui/gfx/codec/png_codec.h

Index: ui/gfx/codec/png_codec.h
diff --git a/ui/gfx/codec/png_codec.h b/ui/gfx/codec/png_codec.h
index ba8c8159c2f01f31ce124ead26e5f29e6397737a..7f2c4efd1eae8bff2ec57fca2b5572812e3b954a 100644
--- a/ui/gfx/codec/png_codec.h
+++ b/ui/gfx/codec/png_codec.h
@@ -96,6 +96,11 @@ class GFX_EXPORT PNGCodec {
                                      bool discard_transparency,
                                      std::vector<unsigned char>* output);
 
+  // Similar to FastEncodeBGRASkBitmap, but with no compression at all.
+  static bool NoCompressEncodeBGRASkBitmap(const SkBitmap& input,
+                                           bool discard_transparency,
+                                           std::vector<unsigned char>* output);
+
   // Call PNGCodec::Encode on the supplied SkBitmap |input|, which is assumed
   // to be kA8_Config, 8 bits per pixel. The bitmap is encoded as a grayscale
   // PNG with alpha used for color intensity. The |output| param is passed