Fix occurrences of "-Wextra-semi-stmt"

Docs-Preview: https://skia.org/?cl=173761
Change-Id: Iefdb91cd28eabb4b01b7b42a4f300b0b4caf05d9
Reviewed-on: https://skia-review.googlesource.com/c/173761
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp
index a92bd6a..ed549b7 100644
--- a/src/codec/SkPngCodec.cpp
+++ b/src/codec/SkPngCodec.cpp
@@ -199,7 +199,7 @@
         case kPngError:
             // There was an error. Stop processing data.
             // FIXME: Do we need to discard png_ptr?
-            return false;;
+            return false;
         case kStopDecoding:
             // We decoded all the lines we want.
             return true;