Revert of change SkDraw and all Blitters to use pixmap instead of bitmap (patchset #6 id:100001 of https://codereview.chromium.org/1148793007/)

Reason for revert:
speculative revert to try to unblock DEPS roll

Original issue's description:
> change SkDraw and all Blitters to use pixmap instead of bitmap
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/c31af44336f5eb4a50e83e76e51962d46c3ed458

TBR=scroggo@google.com,jvanverth@google.com,reed@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1164373003
diff --git a/src/utils/SkTextureCompressor.h b/src/utils/SkTextureCompressor.h
index e31a5ab..e35bc95 100644
--- a/src/utils/SkTextureCompressor.h
+++ b/src/utils/SkTextureCompressor.h
@@ -55,10 +55,10 @@
     int GetCompressedDataSize(Format fmt, int width, int height);
 
     // Returns an SkData holding a blob of compressed data that corresponds
-    // to the pixmap. If the pixmap colorType cannot be compressed using the 
+    // to the bitmap. If the bitmap colorType cannot be compressed using the 
     // associated format, then we return NULL. The caller is responsible for
     // calling unref() on the returned data.
-    SkData* CompressBitmapToFormat(const SkPixmap&, Format format);
+    SkData* CompressBitmapToFormat(const SkBitmap& bitmap, Format format);
 
     // Compresses the given src data into dst. The src data is assumed to be
     // large enough to hold width*height pixels. The dst data is expected to