Remove canvas::NewRaster, and rename surface::NewRasterPMColor to N32Premul

patch from issue 781403002 at patchset 20001 (http://crrev.com/781403002#ps20001)

BUG=skia:
TBR=
re-landing after chrome fixes have landed

Review URL: https://codereview.chromium.org/784223007
diff --git a/tests/SkResourceCacheTest.cpp b/tests/SkResourceCacheTest.cpp
index 0e94175..e1f8a65 100644
--- a/tests/SkResourceCacheTest.cpp
+++ b/tests/SkResourceCacheTest.cpp
@@ -11,6 +11,7 @@
 #include "SkDiscardableMemoryPool.h"
 #include "SkGraphics.h"
 #include "SkResourceCache.h"
+#include "SkSurface.h"
 
 static const int kCanvasSize = 1;
 static const int kBitmapSize = 16;
@@ -27,8 +28,8 @@
 
 // Draw a scaled bitmap, then return true iff it has been cached.
 static bool test_scaled_image_cache_useage() {
-    SkAutoTUnref<SkCanvas> canvas(
-            SkCanvas::NewRasterN32(kCanvasSize, kCanvasSize));
+    SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(kCanvasSize, kCanvasSize));
+    SkCanvas* canvas = surface->getCanvas();
     SkBitmap bitmap;
     bitmap.allocN32Pixels(kBitmapSize, kBitmapSize);
     bitmap.eraseColor(0xFFFFFFFF);