add new copyTo version to SkBitmap, which takes SkColorType

BUG=skia:
R=scroggo@google.com, halcanary@google.com, bsalomon@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/171723007

git-svn-id: http://skia.googlecode.com/svn/trunk@13553 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/skimage_main.cpp b/tools/skimage_main.cpp
index f5a2b3d..d34d57c 100644
--- a/tools/skimage_main.cpp
+++ b/tools/skimage_main.cpp
@@ -164,7 +164,7 @@
         return true;
     }
 
-    if (bm.config() == SkBitmap::kARGB_8888_Config) {
+    if (bm.colorType() == kPMColor_SkColorType) {
         // First attempt at encoding failed, and the bitmap was already 8888. Making
         // a copy is not going to help.
         return false;
@@ -172,7 +172,7 @@
 
     // Encoding failed. Copy to 8888 and try again.
     SkBitmap bm8888;
-    if (!bm.copyTo(&bm8888, SkBitmap::kARGB_8888_Config)) {
+    if (!bm.copyTo(&bm8888, kPMColor_SkColorType)) {
         return false;
     }
     return SkImageEncoder::EncodeFile(filename.c_str(), bm8888, SkImageEncoder::kPNG_Type, 100);