Copy src in SkDrawLooper::computeFastBounds().

src/core/SkDrawLooper.cpp

Index: src/core/SkDrawLooper.cpp
diff --git a/src/core/SkDrawLooper.cpp b/src/core/SkDrawLooper.cpp
index d18d12710abd6f2a5c12987a873ae2688554e5c8..1af68a22892d39a524a50f4399fdf243febd275d 100644
--- a/src/core/SkDrawLooper.cpp
+++ b/src/core/SkDrawLooper.cpp
@@ -32,8 +32,11 @@ bool SkDrawLooper::canComputeFastBounds(const SkPaint& paint) const {
     return true;
 }
 
-void SkDrawLooper::computeFastBounds(const SkPaint& paint, const SkRect& src,
+void SkDrawLooper::computeFastBounds(const SkPaint& paint, const SkRect& s,
                                      SkRect* dst) const {
+    // src and dst rects may alias and we need to keep the original src, so copy it.
+    const SkRect src = s;
+
     SkCanvas canvas;
     SkSmallAllocator<1, 32> allocator;
     void* buffer = allocator.reserveT<SkDrawLooper::Context>(this->contextSize());