Revert[2] SkDraw and all Blitters to use pixmap instead of bitmapi

This reverts commit b3f0ec9f9967da2f80f0d842cb7fd53617b48de3.

BUG=skia:

Review URL: https://codereview.chromium.org/1168303006
diff --git a/src/core/SkAAClip.cpp b/src/core/SkAAClip.cpp
index e55451e..19e94c8 100644
--- a/src/core/SkAAClip.cpp
+++ b/src/core/SkAAClip.cpp
@@ -1297,7 +1297,7 @@
     void blitMask(const SkMask&, const SkIRect& clip) override
         { unexpected(); }
 
-    const SkBitmap* justAnOpaqueColor(uint32_t*) override {
+    const SkPixmap* justAnOpaqueColor(uint32_t*) override {
         return NULL;
     }
 
@@ -2219,6 +2219,6 @@
     } while (y < stopY);
 }
 
-const SkBitmap* SkAAClipBlitter::justAnOpaqueColor(uint32_t* value) {
+const SkPixmap* SkAAClipBlitter::justAnOpaqueColor(uint32_t* value) {
     return NULL;
 }