Assert when running SampleApp with msaa 16 on Windows 10

Trivial: skip calling SkWGLExtensions::selectFormat with 0 elements,
 and handle if called.

BUG=4529

Review URL: https://codereview.chromium.org/1427583007

diff --git a/src/utils/win/SkWGL_win.cpp b/src/utils/win/SkWGL_win.cpp
index bc22795e2ffb3bb57f2240b492f92004ca512a55..5afcae94cec4f82303923d6bfb0b2ccd056cd64c 100644 (file)
--- a/src/utils/win/SkWGL_win.cpp
+++ b/src/utils/win/SkWGL_win.cpp
@@ -126,6 +126,9 @@ int SkWGLExtensions::selectFormat(const int formats[],
                                   int formatCount,
                                   HDC dc,
                                   int desiredSampleCount) const {
+    if (formatCount <= 0) {
+        return -1;
+    }
     PixelFormat desiredFormat = {
         0,
         desiredSampleCount,