Revert of Rename kPMColor_SkColorType to kN32_SkColorType. (https://codereview.chromium.org/227433009/)

Reason for revert:
Chrome's side of define changes not easy to figure out quickly. Reverting this for DEPS roll for now.

Original issue's description:
> Rename kPMColor_SkColorType to kN32_SkColorType.
>
> The new name better represents what this flag means.
>
> BUG=skia:2384
>
> Committed: http://code.google.com/p/skia/source/detail?r=14117

R=reed@google.com, scroggo@google.com
TBR=reed@google.com, scroggo@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2384

Author: bensong@google.com

Review URL: https://codereview.chromium.org/234833003

git-svn-id: http://skia.googlecode.com/svn/trunk@14149 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tools/skimage_main.cpp b/tools/skimage_main.cpp
index e5610ea..5e5953e 100644
--- a/tools/skimage_main.cpp
+++ b/tools/skimage_main.cpp
@@ -164,7 +164,7 @@
         return true;
     }
 
-    if (bm.colorType() == kN32_SkColorType) {
+    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, kN32_SkColorType)) {
+    if (!bm.copyTo(&bm8888, kPMColor_SkColorType)) {
         return false;
     }
     return SkImageEncoder::EncodeFile(filename.c_str(), bm8888, SkImageEncoder::kPNG_Type, 100);