Fix SkImageInfo::computeByteSize underflow

Bug: chromium: 819616
Change-Id: I9d4c079ad93518e45739fbb7d1abc32dedbb9c26
Reviewed-on: https://skia-review.googlesource.com/132281
Auto-Submit: Adrienne Walker <enne@chromium.org>
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/core/SkImageInfo.cpp b/src/core/SkImageInfo.cpp
index 7e08be2ab9..a743dbce70 100644
--- a/src/core/SkImageInfo.cpp
+++ b/src/core/SkImageInfo.cpp
@@ -65,7 +65,7 @@ size_t SkImageInfo::computeByteSize(size_t rowBytes) const {
         return 0;
     }
     SkSafeMath safe;
-    size_t bytes = safe.add(safe.mul(fHeight - 1, rowBytes),
+    size_t bytes = safe.add(safe.mul(safe.addInt(fHeight, -1), rowBytes),
                             safe.mul(fWidth, this->bytesPerPixel()));
     return safe ? bytes : SK_MaxSizeT;
 }