Ignore backspace when appending to the filter string in SampleApp. Fixes a bug on Windows where the…

samplecode/OverView.cpp

Index: samplecode/OverView.cpp
diff --git a/samplecode/OverView.cpp b/samplecode/OverView.cpp
index d7633452bc3c98e2864564e1ab59b14640ea7576..8520f5700051bf1932fab02a7fb5ab5e0685d230 100644
--- a/samplecode/OverView.cpp
+++ b/samplecode/OverView.cpp
@@ -59,7 +59,9 @@ protected:
         }
         SkUnichar uni;
         if (SampleCode::CharQ(*evt, &uni)) {
-            fMatchStr.appendUnichar(uni);
+            if (uni >= ' ') {
+                fMatchStr.appendUnichar(uni);
+            }
             this->inval(nullptr);
             return true;
         }