add SkCanvas constructor that explicitly creates no_config with dimensions

BUG=skia:
R=scroggo@google.com, halcanary@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/137833016

git-svn-id: http://skia.googlecode.com/svn/trunk@13272 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/utils/SkDumpCanvas.cpp b/src/utils/SkDumpCanvas.cpp
index dabf0d7..5f3a572 100644
--- a/src/utils/SkDumpCanvas.cpp
+++ b/src/utils/SkDumpCanvas.cpp
@@ -163,15 +163,9 @@
 
 ///////////////////////////////////////////////////////////////////////////////
 
-static SkBitmap make_wideopen_bm() {
-    static const int WIDE_OPEN = 16384;
+#define WIDE_OPEN   16384
 
-    SkBitmap bm;
-    bm.setConfig(SkBitmap::kNo_Config, WIDE_OPEN, WIDE_OPEN);
-    return bm;
-}
-
-SkDumpCanvas::SkDumpCanvas(Dumper* dumper) : INHERITED(make_wideopen_bm()) {
+SkDumpCanvas::SkDumpCanvas(Dumper* dumper) : INHERITED(WIDE_OPEN, WIDE_OPEN) {
     fNestLevel = 0;
     SkSafeRef(dumper);
     fDumper = dumper;