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/effects/SkLayerRasterizer.cpp b/src/effects/SkLayerRasterizer.cpp
index 8403d06..d3e112c 100644
--- a/src/effects/SkLayerRasterizer.cpp
+++ b/src/effects/SkLayerRasterizer.cpp
@@ -116,12 +116,9 @@
     }
 
     if (SkMask::kJustComputeBounds_CreateMode != mode) {
-        SkDraw          draw;
-        if (!draw.fDst.reset(*mask)) {
-            return false;
-        }
-
+        SkBitmap        device;
         SkRasterClip    rectClip;
+        SkDraw          draw;
         SkMatrix        translatedMatrix;  // this translates us to our local pixels
         SkMatrix        drawMatrix;        // this translates the path by each layer's offset
 
@@ -131,6 +128,9 @@
         translatedMatrix.postTranslate(-SkIntToScalar(mask->fBounds.fLeft),
                                        -SkIntToScalar(mask->fBounds.fTop));
 
+        device.installMaskPixels(*mask);
+
+        draw.fBitmap    = &device;
         draw.fMatrix    = &drawMatrix;
         draw.fRC        = &rectClip;
         draw.fClip      = &rectClip.bwRgn();