Revert of Revert of Rename kPMColor_SkColorType to kN32_SkColorType. (https://codereview.chromium.org/234243002/)

Reason for revert:
Want to reland the original CL.

Original issue's description:
> Revert of Rename kPMColor_SkColorType to kN32_SkColorType. (https://codereview.chromium.org/227433009/)
>
> Reason for revert:
> breaking the Chrome deps roll.
> http://build.chromium.org/p/chromium.linux/builders/Linux%20GN%20%28dbg%29/builds/839/steps/compile/logs/stdio
>
> 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
>
> TBR=reed@google.com,scroggo@google.com
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:2384
>
> Committed: http://code.google.com/p/skia/source/detail?r=14144

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

Author: scroggo@google.com

Review URL: https://codereview.chromium.org/235523003

git-svn-id: http://skia.googlecode.com/svn/trunk@14156 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/SkAlphaThresholdFilter.cpp b/src/effects/SkAlphaThresholdFilter.cpp
index f938ba6..205e9a9 100644
--- a/src/effects/SkAlphaThresholdFilter.cpp
+++ b/src/effects/SkAlphaThresholdFilter.cpp
@@ -306,9 +306,9 @@
 bool SkAlphaThresholdFilterImpl::onFilterImage(Proxy*, const SkBitmap& src,
                                                const Context& ctx, SkBitmap* dst,
                                                SkIPoint* offset) const {
-    SkASSERT(src.colorType() == kPMColor_SkColorType);
+    SkASSERT(src.colorType() == kN32_SkColorType);
 
-    if (src.colorType() != kPMColor_SkColorType) {
+    if (src.colorType() != kN32_SkColorType) {
         return false;
     }