change SkDraw and all Blitters to use pixmap instead of bitmap

src/effects/SkLayerRasterizer.cpp

Index: src/effects/SkLayerRasterizer.cpp
diff --git a/src/effects/SkLayerRasterizer.cpp b/src/effects/SkLayerRasterizer.cpp
index d3e112c3a4b836118be46258c5f3d1b9fb181ab3..247ee3d2db799410b0c971eab43dcd8823b91fce 100644
--- a/src/effects/SkLayerRasterizer.cpp
+++ b/src/effects/SkLayerRasterizer.cpp
@@ -116,7 +116,6 @@ bool SkLayerRasterizer::onRasterize(const SkPath& path, const SkMatrix& matrix,
     }
 
     if (SkMask::kJustComputeBounds_CreateMode != mode) {
-        SkBitmap        device;
         SkRasterClip    rectClip;
         SkDraw          draw;
         SkMatrix        translatedMatrix;  // this translates us to our local pixels
@@ -128,9 +127,9 @@ bool SkLayerRasterizer::onRasterize(const SkPath& path, const SkMatrix& matrix,
         translatedMatrix.postTranslate(-SkIntToScalar(mask->fBounds.fLeft),
                                        -SkIntToScalar(mask->fBounds.fTop));
 
-        device.installMaskPixels(*mask);
-
-        draw.fBitmap    = &device;
+        if (!draw.fDst.reset(*mask)) {

[scroggo, 2015/06/08 15:21:38]

Again, it seems like we could move this error exit case earlier.

[reed1, 2015/06/08 17:11:01]

Done.

+            return false;
+        }
         draw.fMatrix    = &drawMatrix;
         draw.fRC        = &rectClip;
         draw.fClip      = &rectClip.bwRgn();