Replace uses of GrAssert by SkASSERT.

R=bsalomon@google.com

Review URL: https://codereview.chromium.org/22850006

git-svn-id: http://skia.googlecode.com/svn/trunk@10789 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkXfermode.cpp b/src/core/SkXfermode.cpp
index 020ea48..587b0b9 100644
--- a/src/core/SkXfermode.cpp
+++ b/src/core/SkXfermode.cpp
@@ -960,7 +960,7 @@
             } else {
                 dstColor = builder->dstColor();
             }
-            GrAssert(NULL != dstColor);
+            SkASSERT(NULL != dstColor);
 
             // We don't try to optimize for this case at all
             if (NULL == inputColor) {