Adding a flush method to SkCanvas

BUG=http://code.google.com/p/skia/issues/detail?id=467
REVIEW=http://codereview.appspot.com/5600044/
TEST=gm uses the new code path on all its test cases



git-svn-id: http://skia.googlecode.com/svn/trunk@3102 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index c1304a2..7be822a 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -287,9 +287,7 @@
         }
         SkAutoUnref canvasUnref(canvas);
         invokeGM(gm, canvas);
-        if (deferred) {
-            canvas->getDevice()->accessBitmap(false); // trigger a flush
-        }
+        canvas->flush();
     } else {  // GPU
         if (NULL == context) {
             return ERROR_NO_GPU_CONTEXT;