Revert of Remove FORMAT_RGB from gfx::PngCodec

ui/gfx/codec/png_codec.cc

Index: ui/gfx/codec/png_codec.cc
diff --git a/ui/gfx/codec/png_codec.cc b/ui/gfx/codec/png_codec.cc
index fe4020596fc9c3ba32609719060a727554b07e81..69a00c19449403b6a3853627217af1e18b838cfc 100644
--- a/ui/gfx/codec/png_codec.cc
+++ b/ui/gfx/codec/png_codec.cc
@@ -206,6 +206,9 @@
   // Pick our row format converter necessary for this data.
   if (!input_has_alpha) {
     switch (state->output_format) {
+      case PNGCodec::FORMAT_RGB:
+        state->output_channels = 3;
+        break;
       case PNGCodec::FORMAT_RGBA:
         state->output_channels = 4;
         png_set_add_alpha(png_ptr, 0xFF, PNG_FILLER_AFTER);
@@ -222,6 +225,10 @@
     }
   } else {
     switch (state->output_format) {
+      case PNGCodec::FORMAT_RGB:
+        state->output_channels = 3;
+        png_set_strip_alpha(png_ptr);
+        break;
       case PNGCodec::FORMAT_RGBA:
         state->output_channels = 4;
         break;
@@ -627,6 +634,12 @@
   int input_color_components, output_color_components;
   int png_output_color_type;
   switch (format) {
+    case PNGCodec::FORMAT_RGB:
+      input_color_components = 3;
+      output_color_components = 3;
+      png_output_color_type = PNG_COLOR_TYPE_RGB;
+      break;
+
     case PNGCodec::FORMAT_RGBA:
       input_color_components = 4;
       if (discard_transparency) {